Why do you post such a question after you have done the deal. If we think you did bad would you cancel the deal?
I think a deal is a deal and you should ask these questions before you make them not after. Don't look back.
I could say; That is a real bargain. I would have paid you double that price. Would that change anything other than making you feel bad? I wouldn't ask. the deal is done. Close your eyes and get it over with.
Just my 2 cents.