Math is not a physical science -- and you can get stunning breakthroughs without anything except a quiet room, a pad of paper, a pencil, and a trash can. (old joke: /s/math/philosophy and remove the trash can!)
This is not true if you're a microbiologist.
Money vastly expands the scope of work you can do, but breaking new ground is often less expensive than making minor refinements to well understood areas.
PS: The real risk is will likely will go 20+ years without finding anything, but if you have tenure that should not be a problem.
Kitting out a lab to do publishable work in a lot of fields right now is just jaw-droppingly expensive.
Further, used equipment can often be vastly cheaper.
Honestly, time and consumables really are the biggest issues.
You will not publish anything good enough to get tenure if all you have is widefield and a lamp in basically any biomedical field.
Further, the assumption is this is someone that has tenure but not funding and is thus able to take long shot risks. Think designing an artificial intestines for microbiome research, not yet another paper using E. coli.
Florescent microscopes are in the low six figures and others are much more expensive. A confocal microscope is typically several hundreds of thousands of dollars, potentially approaching $1M if it has all the bells and whistles. Super-res and high-throughput imaging can also consume essentially infinite amounts of money.
You could probably get a usable brightfield microscope for around a $1,000 but realistically, you're not publishing much with that alone.