I dont really have a price I would stop buying bitcoin because the price of bitcoin is relative. I would only look at bitcoin if I saw there being no fundamental future for bitcoins to exist. As long as bitcoin has future potential, I would buy bitcoins at any price.
Good thing that you are not considering the value of bitcoin, at some point at its current price now although it is high but eventually would rise more than that in the future. But for me, if the price per btc would be $50k again, I am gonna trade again. But if the price will continue to rise I am gonna trade but just a few btc.