I think it is great to do things that are good bang for your buck. For me that was when I was visiting my family my sister picking out a $7 box of hair color and her coloring and cutting my hair. Often when she cuts my hair I get a lot of compliments, more often my general appearance (that I looked good, did I go to the beach, etc??). I think it's because what she does is subtle but knows how to cut my hair so it's flattering to my face.
Keeping fit (I am NOT right now but want to return to) is a good bang for buck because you better fit your clothes, posture, stress relief, circulation etc.
I can even imagine for some- because it is a one time thing- getting electrolysis, eyeliner tattoo, even some forms of plastic surgery, because it is more of a one-time expense that pro-rates itself. Not for me, but individuals vary.
What I don't get is spending money on makeup or treatments that are temporary that have to be paid for over and over again. It would have to be extremely cheap (like my queen helen mint julep face mask) or something like a good spf face sunscreen to feel spending on those things are worth it.
ETA- I also agree, that women's looks are so judged by their appearance, it ALSO rubs me the wrong way when men give the compliment that you look good without makeup. Yes I've never worn makeup and am not going to start now (other than blemish concealer and tinted lip balm). But where were were you doing all the decades of heavy peer and media pressure to have the perfect hair, skin, makeup, grooming etc all the time? Now it just feels a slightly different perhaps higher bar of yeah, you STILL have to look great, but you are not supposed to look like you are trying hard or using artificial enhancement or if you do, so subtly other people don't realize you are.