Pay-What-You-Can allows your customers to determine the amount they pay for one of your products.
Select Products from your Simplero Dashboard
From the Products tab, select the product you want to offer the subscription price
Go to Settings
Select the Pricing tab
Add a single payment price:

Complete all relevant fields for your price such as Name, Label, Payment, etc. Set the price to whatever your minimum price is (can be 0, or any other amount).

Toggle ON the Allow donations option:

Enable the price by clicking the Live toggle at the far right corner of that price box:

Now when someone selects that price option for the order form, they can determine how much they’ll pay.