How to structure purchase price for enterprise procurement?

Let's say I sell my software for $5000/yr on-prem and someone at a large public enterprise wants to use it. They initiate procurement via a third-party software vendor.

I haven't done many of these before and always feel like I'm leaving money on the table. What is the best way to structure the enterprise quote when dealing with a procurement firm?

• Do I charge a one-time license fee?
• Is there an annual maintenance fee? What would it be as a % of original cost?
• Should I add things like SLA on top of the original (probably way too low) $5k/yr quote?
• Or should I just charge a flat $X per year and leave out those details?
• Any other fees or opportunities that I'm missing?