Russell, I may be wrong, but in my experience the charges are based on the type of account the person you are paying has with PayPal. When I had the Personal account, the first few transactions were free, and then the service charge kicked in. Since I use it for the raffles here on the site, I got the Business account. There, I can have all the transactions I want. There is always a service charge, but the % is less than the one charged to a Personal account.
I hope this helps.