You missed the first part of his response. If you're only hitting under 100k you're probably a newer player. The champions is a long-term thing, if you're low level you're going to be sucking it up chipping away at them.
Once you get to splatters archipelago the boss drops EXP books, so there is an offset for the cost of upgrading your girls. If you're stuck on one level for a long time then you should have girls to match the positions, and you can focus on leveling up those girls specifically, buy out the EXP books when the market refreshes.
Also, I have a full time job as well, but I still play from my phone during the day, on scheduled breaks... because I would NEVER EVER EVER hide in the bathroom and play HH!