When would you build a custom LWC vs use an AppExchange component?

Build-vs-buy decision for UI. The trade-offs:

Buy (AppExchange) when:

• The component solves a standard, common problem (file uploader, calendar, signature pad, charting library).
• The vendor is established and has a track record.
• Time-to-market matters more than customisation.
• Maintenance of the bespoke component would be ongoing.
• Cost is acceptable — many components are free or cheap.

Build when:

• The use case is specific to your business — generic components don't fit.
• Tight integration with custom data model required.
• Performance matters and you can build faster than the off-the-shelf option.
• Security/compliance requires code your team controls.
• Cost over time of licensing exceeds dev cost.
• You need it to be deeply customisable in ways the vendor doesn't support.

Hidden costs of buying:

• Lock-in — once integrated, replacing is expensive. Choose vendors with clean APIs and clear deprecation policies.
• Upgrade pain — vendor's release cycle may not match yours; major version changes can break.
• Customisation limits — vendors often expose less customisation than you eventually need.
• Performance — managed package code adds load; multiple installed components compound.
• Security review status — un-reviewed packages carry risk.

Hidden costs of building:

• Maintenance — bugs, browser compatibility, accessibility, ongoing development.
• Feature creep — what starts as "small custom component" grows.
• Knowledge concentration — risk if the developer leaves.

Hybrid approach (often best):

Use AppExchange for the heavy lifting (charting, rich-text editor) and wrap with custom components for branding / business logic. Get the vendor's robustness with your specific UX.

Decision framework:

1. Search the AppExchange first. If a 5-star reviewed component exists, default to it.
2. Trial it in a sandbox. Confirm it works for your use case before committing.
3. Estimate maintenance cost of building over 3 years.
4. Consider exit cost — if you build, can you switch later? If you buy, can you migrate to building?

For visual primitives (datatable, picker, chart) — usually buy. For business-specific UX — usually build.