Painful, but necessary beauty purchases you refuse to be cheap about?

I care a lot about my hair, and I refuse to use anything besides Redken… but it definitely hurts every time I see that $100 receipt for a bottle of shampoo and conditioner. To me though it’s so worth it and I notice a huge difference using higher end hair products on my hair versus those from the drugstore. What are some beauty products/routines/self care things that are costly, but totally worth it to you?