Do you mix with monitors?
How much spend on them?
Yes I do!
I use Yamaha HS50M monitors and they have served me well. I do like to test other environments too (particularly for podcast production). I’ll often check on iPhone with one earbud, on a Sonos Playbar and also in on our in car audio system too.
Almost every monitor is good when you get familiar with the sound. I spend a lot of time, going from my friends studio, to my car, and my room to get to know my monitors, and I still often switch from them to poor cardboard tv speakers that my father take out from some old tv. If mix sounds good there, then it is good.