"overprice" --- did you mean 'overcharge"?
I have heard the word overpriced, the past passive participle as an adjective (e.g. an overprice stock), but I am not sure I have ever heard it used as a present active verb.
Overprice isn't a word in English. Overcharge would be a better word to use
Overprice is a word but we use it for the thing being sold. Overcharge or rip off for the buyer.
rip-off is THE word.