Maybe Visiolist should look into a credit system.
 
Currently a referral from a user will still pay the normal price for the Toplist, but the referee will receive a cash-back for linking them to Visiolist.
 
What if rather then linking for a cash reward, they where linked for a point system that meant when someone was refereed you could offer Visiolist at a discounted price and still maintain the profit, simply using points to buy paid plugins or other benefits. This is more like a 'Gift Card' style of rewards since it still has to be used on Visiolist. I doubt anyone would complain as there are still using the Toplist software anyway.
 
Examples of credit spending could be:
 
- Renew Visiolist License
 
- Upgrade Visiolist License
 
- Remove Branding
 
- Buy possible future premium plugins
 
I understand making a whole new payment system would cost time and possibly money, but if you increase the price and still offer a discounted version, it 1 looks better to the customer who thinks they are getting a better deal and 2 allows users to gain without the need for a cash return.
 
Just a small suggestion.