Not a gun sale but a company sale of a controlling interest in shares.

The seller (the managing director) complained to the new owner (the Chairman), "We have been getting weekly enquiries into controlling interest in this company since we sold to you, and all of them have been for more money!"

The owner replied: "You received 100% of what you asked for, and we paid you every cent you asked for."

Sums it up in a free market economy.

Same for guns.

You pay what you want. You receive what you offer it for. In a transaction with a sale and a purchase. No one is forced to do anything.