People on CL do it all the time. However people on CL do lots of things that annoy me, especially employers. Oh well.
It's kinda weird when it is posted on here though. I guess maybe they have it listed on other sites/forums and don't want to change prices on stuff and have someone realize it's cheaper if you inquire on a different site/forum.
I might've just said that confusingly but if you were to post a part for a certain amount of money, then post that same part on a different forum and maybe lowered the price down because no one wants to buy it or you just don't remember how much you originally posted the price for, people could view that forum and see/call you out on it.