Nobody's buying a 3d printer just to print a fan. This is useful for people who already own one.

A solvent chamber for smoothing a fan blade could be just a plastic box from the dollar store. A kilogram of filament could cost you less than $15, and the fan itself would use up maybe 15 grams of that. The printing time depends greatly on printer and settings, but that's idle time anyway, not time spent doing actual work. You can do other things in the meantime.

Your argument is like factoring in the cost of buying a car to buy groceries and cook at home instead of eating at a restaurant.

This was not advice for your average gamer, getting another fan for their PC build. It is more for the "I have this weird shape and geometry where I need to attach a fan with such weird geometries that their is no commercial viable alternative" crew.

Also a solvent chamber is just a jar ideally with lid but even thats optional.