Business Central is licensed per named user, per month, through a Microsoft partner. There are three licence types: Essentials and Premium for full users who run finance and operations, and Team Members for people who mostly read data and approve things. You buy the number of each that matches how people actually use the system, not one licence for everyone.
Licence prices are set by Microsoft and are identical whichever partner you buy through. That means shopping around on licence cost achieves very little. What genuinely changes your total cost is how the system is scoped and implemented, how many full users you really need, and what your support arrangement looks like after go-live.
The tier decision is simpler than most vendors make it sound. Premium exists for organisations that manufacture products or run a field service operation. Everyone else is on Essentials, and moving up later is a licence change rather than a re-implementation, so there is no need to over-buy at the start.