What drives the cost
The number of users, and how they work. Someone who spends the whole day at the office on quotes and orders uses Lean differently from an employee who registers hours on the shop floor.
The areas you use. Sales, purchasing, inventory, production, planning, invoicing, projects: the more of your operation runs in Lean, the bigger the project.
How far your way of working differs. Many processes can be handled through set-up. What is truly specific to your company sometimes needs custom development.
Your data. How much data you bring along, from which system, and how clean it is.
Integrations and portals. Which packages Lean has to work with, and which outside parties look in through a portal.