You're probably not counting all the overhead, particularly from heavy equipment. Skidsteers, dump trailers, stump grinders, as well as all the oversized/towing capable trucks to haul those machines around. All of that equipment needs maintenance and fuel, as well.

The expensive part is usually just showing up ready to work, with a marginal cost for each additional tree. If you had 15 trees taken down in one day, the cost per tree would work out to seem much more reasonable.

My neighbors were having a bunch of tree work done, and I asked the supervisor what it would cost to take a big dead one down on my property. I planned to do it myself, so I had a strong haggling position, and I got him to $400, which felt worth it to save me a day's worth of hard labor. If they weren't already onsite with all the gear, that would've been $2K+ easy.