Build vs Buy Decision Framework for Engineering Leaders
Quick Answer
Building in-house software requires 12-36 months and costs $500,000-2,000,000+ in salary and infrastructure, while buying solutions averages $50,000-500,000 annually with immediate implementation. The optimal decision depends on strategic value, differentiation impact, and cash runway—build only if the solution is core to competitive advantage and your runway supports the timeline.
What Are the Hidden Costs of Building In-House?
The nominal cost of building includes engineering salary ($150,000-200,000/year) and infrastructure ($5,000-20,000/month). Over 18 months to launch, this appears to be $300,000-$600,000.[1]
However, hidden costs include: opportunity cost (engineers distracted from revenue-generating work), delay cost (revenue loss while building), quality assurance and bug fixing, maintenance and technical debt, and scalability improvements as customer needs evolve. These hidden costs often equal or exceed direct development costs.
What's the Real Timeline for Building Custom Solutions?
Most engineering leaders underestimate building timelines by 30-50%.[2] A project estimated at 12 months typically requires 16-18 months when accounting for scope creep, integration challenges, and testing.
This timeline matters because it delays revenue impact. Waiting 18 months for an in-house CRM while competitors deploy solutions in 1-2 months creates competitive disadvantage. The timeline difference compounds if the solution addresses customer needs affecting retention.
How Do You Calculate True Cost of Ownership (TCO)?
TCO includes: Direct development cost (engineering salary), Infrastructure and hosting, Maintenance and bug fixes, Future enhancements and features, Operational overhead (support, training, documentation), and Opportunity cost of engineering time.
Example build scenario:
- 2 engineers × $180,000/year × 1.5 years = $540,000
- Infrastructure/hosting: $15,000/year × 1.5 = $22,500
- Maintenance and enhancements (post-launch): $100,000/year
- Total 3-year cost: $700,000+
Comparable buy scenario:
- Annual SaaS cost: $200,000
- Implementation: $50,000 (one-time)
- Training and support: $20,000/year
- Total 3-year cost: $670,000
The costs are surprisingly comparable when properly calculated, but the buy scenario provides immediate revenue impact while the build scenario requires patience.
What Questions Determine If Building Is Justified?
Critical questions to ask before building:[3]
- Is this solution core to our competitive advantage?
- Can existing solutions be customized to meet 80% of requirements?
- Do we have engineering runway (both time and budget) for 18-24 months?
- What's the revenue impact of a 6-month delay?
- Can we buy now and build in-house later if needed?
If the answer to #1 is "no" or #3 is "no," buying is almost always correct. If #1 is "yes" and #3 is "yes," building may be justified.
When Does Building Create Competitive Advantage?
Building is most justified when the solution represents core intellectual property or significant competitive differentiation.[4] Examples include: Proprietary recommendation algorithms (Netflix builds recommendation engine), specialized financial models (Bloomberg builds financial terminals), or unique user experiences (Apple builds custom OS).
Building is rarely justified for commodity software: CRM, HR management, accounting, email, file storage. These markets have mature solutions; custom building wastes engineering resources.
What About Hybrid Approaches—Buy Now, Build Later?
The hybrid approach buys a solution to address immediate needs, then builds custom in-house if competitive advantage justifies investment. This approach provides:[5]
- Immediate revenue impact and customer success
- Time to validate product-market fit before investing in custom building
- Comparison point for evaluating custom solution performance
- Ability to integrate buy solution with in-house tools
Many successful companies use this approach: Starting with Salesforce for CRM, then building custom sales tools once they understand requirements and have revenue to fund development.
How Do You Account for Vendor Risk in Buy Decisions?
Key vendor risks include: Vendor lock-in (expensive migration if switching solutions), Price increases over time (15-30% annual increases are common for SaaS), Discontinuation risk (vendor shuts down product), Integration limitations (vendor APIs may not meet needs), and Security and data privacy concerns.[6]
Mitigate vendor risk by: Negotiating multi-year pricing locks, requiring data export in open formats, ensuring SOC 2 or ISO 27001 compliance, evaluating multiple vendors, and designing integrations for switching flexibility.
What's the Opportunity Cost of Engineering Time?
This is the most underestimated factor in build decisions. Two senior engineers assigned to custom CRM for 18 months can't work on product improvements, customer features, or new revenue-generating initiatives.[7]
Quantify this: If your company targets 40% annual growth, the 18-month engineering diversion likely costs $2-5M in lost revenue or delayed growth. This opportunity cost is often larger than the $500,000 direct build cost.
How Do Technical Debt and Maintenance Factor Into Build Decisions?
In-house built solutions require ongoing maintenance (fixing bugs, adapting to platform changes, scaling infrastructure).[8] Industry estimates suggest 20-30% of engineering time goes to maintaining existing systems rather than building new features.[9]
A custom-built solution might consume 0.5-1 FTE annually for maintenance. Over 5 years, this represents $750,000-1,500,000 in salary cost plus other overhead. Bought solutions shift this burden to vendors.
Should You Build If You Have the Engineering Capacity?
No. Having engineering capacity doesn't make building optimal. The question is: Is building the best use of that capacity?[10] Often, even with extra capacity, deploying engineers on product features, customer success, or infrastructure improvements delivers more business value than building commodity software.
The only exception is when building is explicitly part of your competitive strategy and you have both capacity and runway to execute successfully.
Relevant Calculators
- https://products.investorsam.com/products/build-vs-buy-calculator
- https://products.investorsam.com/products/founder-salary-affordability-calculator
- https://products.investorsam.com/products/founder-salary-affordability-calculator
- https://products.investorsam.com/products/real-estate-roi
Frequently Asked Questions
Q: How do you justify building to investors? A: Only justify building if it creates competitive advantage not replicable by competitors. Investors are skeptical of custom building for non-core functions.
Q: What's the best time to build vs buy? A: Build after reaching product-market fit and achieving sufficient revenue (typically $5-10M+ ARR). Early-stage companies almost always should buy.
Q: Can you transition from buying to building? A: Yes, but it's complex. Plan for 6-12 months of overlap, parallel systems, and careful data migration. This transition works best after validating competitive advantage.
Q: What if your custom needs are unique? A: Evaluate building only if 1) needs are truly unique (not just seeming unique), 2) the unique aspects create customer value, and 3) you have runway to execute properly.
Sources
[1] McKinsey & Company. "The Build vs. Buy Decision in Software." https://www.mckinsey.com/industries/technology-media-and-telecommunications/
[2] Software Engineering Institute, CMU. "Software Project Management." https://www.sei.cmu.edu/
[3] Reforge. "Technical Decision Making." https://www.reforge.com/
[4] Harvard Business Review. "Build vs. Buy Decisions for Technology." https://hbr.org/
[5] Gartner. "Build vs. Buy vs. Partner Strategy." https://www.gartner.com/
[6] Forrester Research. "Vendor Risk Assessment Framework." https://www.forrester.com/
[7] Boston Consulting Group. "Opportunity Cost in Technology Investment." https://www.bcg.com/
[8] IEEE Computer Society. "Software Maintenance and Evolution." https://www.computer.org/
[9] Copado. "State of DevOps Report." https://www.copado.com/
[10] Stripe Atlas Guides. "Build vs Buy." https://stripe.com/atlas/guides