In your new project, you need a processing core to control your fancy new whizbang device, which can reside on a main board.  The question is: Are you better off buying a commercial processor board or designing your own module?

Just from a dollars and cents perspective, a commercial board will typically cost you a minimum of 3 times the Bill-of-material cost.  For example, if the module you are considering costs $60, you can figure that the manufacturer’s cost is about $20.  Thus, if you were to roll your own module with similar features, you can estimate a similar cost for your own production.

Does saving $40 per module worth the trouble to design your own?  As with every other engineering questions, the answer is “It depends“.

If your plans are to ship 100 devices per year, a $4000 savings per year is chump change and the engineering effort will end up costing you way more than $4000.

If you ship 10,000 per year,  then the savings are more than enough to recoup your development cost.

What about 1000 units per year?  On the face of it, you would save $40,000 per year, but keep in mind that you need to design your board, debug it and also potentially write quite a bit of code to provide the drivers (which would typically be available from a commercial board vendor).

The other big factor in all this is time.  You save a large amount of time if you buy off the shelf.  And occasionally, that trumps everyhing…