Dynamics 365 CRM, which Microsoft also calls Customer Engagement, is not a single product. It is a family of applications - Sales, Customer Service, Field Service and Customer Insights - that share the same data platform. You license each application per named user, per month, through a Microsoft partner, and you buy only the applications each person actually uses.
Two things make the pricing simpler than it first looks. Each application comes in a Professional and an Enterprise tier, so you pick the depth of functionality you need. And the second application for any given user is charged at a reduced attach rate rather than full price, which keeps multi-app deployments affordable.
Licence prices are set by Microsoft and are identical whichever partner you buy through, so 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 licences you really need versus Team Members, and what your support arrangement looks like after go-live.