nope, just click the buying button after prestige and the cost resets.
but I need to know, where to find the savefile of rat clicker 2 on my pc. I had to start the 3rd time, because my browser sometimes somehow empties the cache itself and all my progress is lost
 "Supermechs"){kind=icon}
 "Cheese Factory"){kind=icon}
 "Rat Clicker 2"){kind=icon}