How do I select between an off-the-shelf module and a custom designed RF assembly?

Selecting between an off-the-shelf (OTS) module and a custom designed RF assembly balances the trade-offs of development cost and time versus production cost, performance optimization, and size/weight/power (SWaP). OTS module advantages include: no NRE (development) cost (the module is designed, tested, and qualified by the manufacturer), fast time to market (evaluation and integration take weeks to months versus months to years for a custom design), guaranteed specifications (the manufacturer warrants the module's performance), and available support (the manufacturer provides applications engineering assistance). OTS module disadvantages include: higher per-unit cost (the manufacturer's margin and overhead are included; OTS modules typically cost 2-5x more per unit than the equivalent custom assembly at production volumes), compromise specification (the module is designed for general use, not optimized for the specific application; it may not meet the exact performance requirements or may include unnecessary features that add cost and size), larger size (general-purpose modules include extra filtering, connectors, and features that increase size), and supply dependence (the user depends on the module manufacturer for ongoing supply and support). Custom design advantages include: optimized performance (designed specifically for the application requirements; can achieve higher performance in a smaller package), lower production cost at volume (no manufacturer margin; component cost only; break-even versus OTS typically occurs at 100-1000 units depending on the design complexity), intellectual property ownership (the custom design is the user's IP), and full supply chain control. Custom design disadvantages: significant NRE cost ($50K-$500K+ for a full custom RF module design), long development time (6-18 months from concept to qualified production), and design risk (the custom design may not meet specifications, requiring iteration).