I think I could pass some time on it.
Prices are quite high so we need several runs to buy the first one.
Also, I think they are completely random (a skill will not have the same price in two runs). If it is the case, it makes plans complicated.
I think there is an issue with the timer, sometimes, two or three seconds pass at once.
Also, I did not really understood when the bomb are set. I thought it was each second but maybe not?