The thing I didn't like about many sub-28 class C's was the master bed situation. It's either a corner bed (we had that in our old trailer, didn't really want it again) or the bed needs to be folded up for the slide to close (as appears to be the case with the one you are looking at). This was a dealbreaker for me, as I want to be able to use the full sleeping arrangement with slides in.
I considered levelers to be mandatory when shopping for a used class C, and was somewhat surprised that they are so rare. I looked at many used class C's and only 2 had levelers installed. I lowered my budget by 4k and planned to have them installed aftermarket on whatever I ended up buying. Not a bad way to go really, then you get to choose which brand/model you want.
If I were buying new, I'd certainly add them on as an included option. On a new rig 4k is a pretty small percentage. For me it's nearly 20% of what my rig cost, but it is what it is.
I ended up with a no slide model that has plenty of carrying capacity, so I see no reason not to add jacks. Yes it's costly, but I want them. :C Not everything about RVing has to be rational. :B