BILL's plans are priced per user, per month: Essentials starts at $49, Team runs $65, and Corporate runs $89, each at that same per-seat basis. Melio's floor is free: the Go plan is $0 /free forever, Core adds paid features at $25/mo plus $10/mo per additional user, and Boost runs $55/mo. Every seat added to a BILL account repeats the full per-user rate for that tier; every seat added to Melio Core adds only the smaller additional-user fee on top of one base subscription.
The one difference that decides it
It comes down to per-user cost against integration depth. BILL's pricing scales with headcount, and it earns that cost with integrations built for enterprise accounting stacks: QuickBooks, Sage Intacct, Oracle Netsuite, Microsoft Dynamics, Xero, Acumatica. Melio covers the accounting platforms a smaller team is actually running day to day: QuickBooks Online sync, Xero sync on Core, and QuickBooks Desktop sync on Boost. NetSuite sync only shows up on Melio's top tier, Unlimited, priced at $80/mo, unlimited users: NetSuite sync. If your books already live in Sage Intacct, NetSuite, or Dynamics, BILL is the only one of the two that reaches that deep. If your books live in QuickBooks or Xero and stay there, Melio's sync is enough, and its floor cost is lower than BILL's at any headcount where the per-user math has not yet caught up.
What the per-user math actually does to your bill
The seat fee is the whole story. Every person added to a BILL Essentials, Team, or Corporate account repeats that plan's full per-user rate, so headcount growth and AP spend move together in lockstep. Melio's Core plan charges one base fee of $25/mo and then $10/mo per additional user for each person past the first, a materially flatter curve as a team grows, though it caps out in what it can sync once a business needs NetSuite or a deeper ERP than QuickBooks and Xero. There is no confirmed additional-user fee published for Melio's Go or Boost plans specifically, so do not assume the Core add-on figure carries over to those tiers; Unlimited sidesteps the seat question entirely at $80/mo, unlimited users. See the full cost pattern for per-user pricing across this category in the per-user pricing guide.
Still undecided?
Ask two questions. First: will finance headcount keep growing, or is it steady? A team that keeps adding people is going to keep paying BILL's per-seat fee, so that cost needs to be worth the ERP depth it buys. Second: does the books stack need anything past QuickBooks or Xero? If the answer is Sage Intacct, NetSuite, or Dynamics, BILL is the only one of the two built for that; read the full plan structure at BILL's pricing review. If the answer is no, stay lean and read the full free-to-paid tier breakdown at the free-tier pick's pricing review before committing to a per-seat platform the team will not fully use. For the wider category, the AP automation buyer's guide routes the rest of the decision.