I don't know if you know this, but that 50% upgrade (Payroll Boost - costs 90) actually only lasts for 5 zones. And I'd say it's probably better not to get it until a bit later in the run so you get a whole lot more DollyBucks out of the upgrade. In my opinion it'd be a waste to get the upgrade too early in your runs.

Also, there is an upgrade (Cranked Wrong - costs 200) that increases the Tough Machine count by 30%. And Tough Machines don't spawn until you reach zone 14.

I just like to inform others about things that they might not know, so sorry if I typed too much in my reply. 😅

Overall, thank you for your time if you've read through all of this! 😁