For a solo agent or team under 10 seats, an IDX plugin (Showcase IDX, iHomefinder) on WordPress at $50-$250/mo is the right answer — custom builds at $150K+ never recoup against a single-agent commission stream. BoomTown or kvCORE ($1.5K-$3K/mo base + seat fees) pay off for 10-75 agent teams needing workflow + CRM + lead gen in one. Custom RESO Web API builds cross under kvCORE lifetime cost around month 28-32 for brokerages above ~60 seats, or earlier when differentiated search is a growth lever (iBuyer, investor focus, hyper-local niche). National brokerages and proptech startups almost always build custom because no platform handles 20+ MLS feeds with per-board display rules cleanly.