You bought it already but I still want to answer this :)

Generally speaking, refunds are given when a plugin either totally doesn't work or doesn't do something it is supposed to do as stated in the description.

Unfortunately, because payments go through Paypal giving refunds for anything other than truly legitimate reason is a problem.

Paypal has recently changed its policy and now, in case of refund, Paypal keeps the fee they originally took on the transaction.

So you pay me and Paypal takes 4.4% of my earnings. You ask for a full refund and I give it back, Paypal keeps the 4.4% fee and I'm out of pocket.

What I generally tell potential users who want to know about my plugin is:
1- Feel free to ask me any and all questions you may have before you buy
2- Look at my other plugins and read the comments you will see that I take support very seriously and fix anything that is not working properly

Thank you for reaching out and I hope you will like Instant Page Speed Magic :)