Aggregate User Counts and Pricing Tier Assistance

Good day,

I am in immediate need of some assistance for a spreadsheet that will accommodate handling pricing tiers related to aggregate user growth. Many of the models and solutions that i have received in this forum don't quite deliver what I am looking to achieve, I am hoping for some quick guidance.

Specifically, I need to be able to take the Customer Count (By Month) and calculate the tiered price for that month and the Monthly Service Fee.
if you can help me with this formula, I can use it to calculate the other tiers for setup & integration and customer cost, plus additional user fees.

I have attached a sample file for reference. Tab 1 is the active sheet.
The fields & values for the tiered pricing are highlighted in yellow.
The User/Customer count is highlighted in orange.

Thanks in advance for your assistance!

I am willing to compensate someone for quick assistance....