I don't think it's fair. Whether you should feel guilty depends, IMO, on your financial situation.
I won't buy from you because you don't think it's fair. And you can be stuck with the unsaleable goods you overbought. I'll buy from the guy down the street who is happy I took it off his hands.
And your other argument about it being somehow taboo to bargain for something used for religious purposes is even more ridiculous.
If there were price stickers on each item and not dynamic pricing based on all sorts of arcana, maybe that would fly, but only because bargaining would have been preempted by fair and known prices.