I stumbled on this thread after all 4 of my covers were stolen last week. Glad to hear that the OP probably wasn't a theft victim, but I just wanted to post so that people know that they
do in fact get stolen on occasion.
The guy in the part department at the local service center who sold me the replacements ($100+tax for a set of 4 for the "old" covers) said that while it doesn't happen a lot, someone like me does come in every once in a while looking for replacements. And I'm guessing another chunk of people just decide to go without the covers after theirs are stolen.
Side note... and I would have laughed at this suggestion just a week ago, but now I'm considering using a tie strap to secure the covers to the rims to deter any future theft attempt. I found a way to do it in which the tie strap is pretty well hidden visually, and posted about it in this thread:
Cable tying aero wheel covers