When should I build custom instead of buy an extension?

Q: When should I build custom instead of buy an extension?

Build when one or more of these is true:It’s your competitive moat. Custom B2B credit-check tied to your in-house ERP, proprietary loyalty tiers that map to your customer-segment hierarchy, integration with a private supplier API. If competitors can’t buy the same thing off-the-shelf, you have a reason to build.No extension covers >80% of the requirement without heavy customisation. The 80/20 rule: an extension needs to handle 80% of your need with 20% configuration. If you’re writing more bespoke code than the extension provides, you’re fork-by-stealth — might as well build.You have a Magento dev on retainer and the long-term maintenance cost is acceptable. Custom code costs you on every Magento upgrade for the next 5+ years.The license-plus-implementation cost exceeds the build cost. Sometimes the math is just better. A $2k license + $4k integration + $400/yr renewal × 5 years = $10k. A $7k custom build with $200/yr maintenance × 5 = $8k. Build wins.Buy when the feature is generic, the cheapest license is <30% of dev cost, and 5+ vendors compete on it. Hybrid (the most common answer): buy the extension as a 70-80% starter, fork or extend it via plugins for your custom logic. Saves 60-80% vs full-build.

Question

Accepted Answer

Build when one or more of these is true:

It’s your competitive moat. Custom B2B credit-check tied to your in-house ERP, proprietary loyalty tiers that map to your customer-segment hierarchy, integration with a private supplier API. If competitors can’t buy the same thing off-the-shelf, you have a reason to build.
No extension covers >80% of the requirement without heavy customisation. The 80/20 rule: an extension needs to handle 80% of your need with 20% configuration. If you’re writing more bespoke code than the extension provides, you’re fork-by-stealth — might as well build.
You have a Magento dev on retainer and the long-term maintenance cost is acceptable. Custom code costs you on every Magento upgrade for the next 5+ years.
The license-plus-implementation cost exceeds the build cost. Sometimes the math is just better. A $2k license + $4k integration + $400/yr renewal × 5 years = $10k. A $7k custom build with $200/yr maintenance × 5 = $8k. Build wins.

Buy when the feature is generic, the cheapest license is <30% of dev cost, and 5+ vendors compete on it. Hybrid (the most common answer): buy the extension as a 70-80% starter, fork or extend it via plugins for your custom logic. Saves 60-80% vs full-build.