I've personally always felt that most tools are a good investment, and commonly will get more than just one genre of use.
If you get a sander it works on restoring furniture as well as sanding your 3d printings.
If you get an airbrush it works on your cosplay, airbrush makeup (low PSI), model kits, stencil butterflies on your kid's bedroom wall, food coloring for cake decoration, t-shirt art, flames on your motorcycle gas tank...
But only you know your budget. A $90 airbrush kit from Harbor Freight (or second hand on FB marketplace) might represent less than your fast food budget for the month. Or it might be the difference between in having enough fuel to get to work all month. "Worth it" is largely impacted by your financial stability and your budgeted 'disposable income'.
