I may have missed something before I posted.
I only read the first post in this thread.
I do that very often.
If they want to increase the price over the amount they are advertising it for, they should pull the ad for at least several days before re-posting it at what ever price they think they want for it.
You are correct.
There is no excuse for getting rude because you do not see eye to eye on the value of what is being sold.
From what you've said, my feeling is that there was some underlying reason for the item being offered for sale.
Possibly a financial need forcing the sale of something they're not wanting to sell.
But, I think it boils down to the fact that they did not want to sell it, what ever the reason.
You'll note that they probably still have it.
Thanks for the welcome.