Ok, got the 41st upgrade. It was literally not worth it. In order to hit 160 cursors you'd need about 720'000'000'000 cookies. That many cookies is enough to buy 55 time machines (ideally you'd spread them out to optimize income vs cost, but let's assume that you just bought time machines). That many time machines would bring in 29'333'040 CPS alone. In comparison, 1600 CPS base (160*10 for the bonus) would require 29333040/1600=18333 non-cursor buildings to make the same amount. Balancing everything out until all items cost 720000000000 cookies brings it up to a few thousand or so, well short of the required number. As it is I've only got a few hundred non-cursor buildings. At my current rate it will take about 300 hours to recover the 720'000'000'000 that the upgrade cost. In that same time, 55 time machines would have made 31'679'683'200'000, enough to buy all required cursors 44 times over.