Chairs were a major consideration while setting up a sewing clinic for my 4-H students. I wanted an adjustable chair because of the various heights of the kids. I wanted 5 points of contact to the floor to reduce the "lean-back" potential so prone by active kids. I couldn't afford 4 office chairs in one pop, so I visited the flea market.
I found good chairs, at different vendors, different markets, for $8 and $10. I tried each one to be certain that the backs and seats were adjustable and the wheels rolled easily. The students will make seat covers or pads for the backs and seats so that all chairs in the room will match, also for long term protection.
So, good task chairs, or computer chairs, as they may be known are available at almost disposable prices. Just try them on for size.