How are mobile transactions priced? Are there extra “mobile” fees?

Mobile transactions run through the same interchange-plus pricing you get for the rest of your account. HMS exclusively quotes interchange-plus, not opaque flat-rate bundles. That means you pay the underlying card-network interchange cost plus a small, transparent markup, with no separate “mobile surcharge” just because you’re using a phone. Your proposal will clearly break out per-transaction costs, any monthly account fee, and optional gateway/virtual terminal fees so you know exactly what mobile processing will cost at your volumes.