Single-rooftop independent dealers under $20M annual sales run fine on a DealerSocket + VIN Solutions stack ($800-$2K/mo). CDK or Reynolds DMS makes sense for franchise dealers 2-50 rooftops where OEM warranty claim throughput justifies the $3K-$20K/mo per rooftop. Tekion and Dealertrack pay off for dealer groups wanting modern APIs without full CDK lock-in — typically 5-200 rooftops. Custom platforms win for used-car tech, EV charging networks, and mobility startups where the proprietary data advantage (pricing IP, charging optimization, mobility pricing) drives margin — break-even vs Dealertrack lifetime cost is typically month 24-32 at $100M+ GMV. Above 50 rooftops with multi-OEM franchises, a hybrid (keep DMS for warranty, custom for CRM/analytics) usually wins.