Am I wrong?

If this has gone a few weeks and you have other buyers, I'd pull the plug and move on. If the MO shows up, write "Refused, return to sender" on the envelope. The lack of concern to update is the first red flag to me.

One thing if you sell things that work well, DEADLINES! Give people firm deadlines that if the money isn't here in 3 days, you're out... PERIOD. Especially if you have other buyers waiting.

Sorry to read about the frustration. Selling sometimes take a BUNCH of patience.