I'm not offering to buy it from you. I'm reminding you that our standard policy is to offer refunds minus shipping/handling, which in your case is $75 minus $10 = $65. You're asking $50.
There isn't a single company I know of that offers refunds prior to the item being returned. That's not how it works anywhere. Go buy something at a local store and try that, let us know how it goes. Even Amazon requires shipping confirmation of the returned item WITH inspection at a UPS store prior to the refund being issued, and I'm not Amazon; just a small business.
Furthermore, what you have is now a discontinued product as the kit was updated, yet I'll still honor our refund policy.
If you don't want to get a $65 refund (more, if you ordered the extra valve and easy splice), then you're free to sell it here for $50 instead.