FWIW, the early checkin cost is for assuring that housekeeping makes up the room that one would be occupying first on the list. So you are paying for them to change their normal process to accommodate you. Is that any different than paying for a late check-out? Which I have done.

Twice on a recent trip I got to the hotel early. The first time was after a TATL flight. I asked several weeks ahead of time about an early arrival - not possible and the rooms the night before were fully booked up. When I got to the hotel at 9:30am the clerk asked why I arrived so early. I explained and he said check in is normally 2pm but I will have house keeping arrange your room ASAP, come back at 11:30am. Given that check out was at 10am that gave them time to work with the leaving guests and accommodated me. I went and got some local currency, found a coffee shop, and did some mindless email for a couple of hours. Then came back - worked out fine in this case but had there been a room available the night before I would have booked it and let them know that I would be coming early the next morning.