I think that you need to register as a vendor. What you have just described is the definition of a vendor.
I felt bad posting that I wanted the tank because I could have paid something for it and am not as deserving as some people who I am sure could use it more than me.
That being said it would have had a great home at my dads and put to use rather than lining the pockets of a vendor like you.
As for returning pumps because you weren't happy that typically only applies if the item has been unused you can't use them and then say you are unhappy. That is just shady.
Reminds me of what my friend told me some people do buying close and wearing them then re-attaching the labels with a price gun to return them.