For a 1-5 provider clinic under 1,500 monthly visits, Athenahealth or eClinicalWorks ($140-500/provider/mo + 4-7% of collections) beats custom build every time. Above ~30 providers or 10k monthly visits, a custom HL7/FHIR + Postgres core ($240K-$420K build, $55K/yr ops + BAA tools) crosses under Athena lifetime cost around month 22-26 on pure software spend. Epic only pays off above ~150 beds or when the hospital needs inpatient + ambulatory + revenue cycle in one stack — below that, the $1.2M-$4M implementation plus $250K+/yr certified-consultant dependency dominates TCO. Digital-health startups building RPM, behavioral health, or specialty workflows almost always win on custom because no SaaS templates match the clinical logic — documented 35-40% clinician-time savings on focused workflows.