You don't mention the type of bike, how old it is, how hard it has been used since last tune up or how long that has been.

If both wheels needed a lot of truing work, hub/bb/headset, bearings needed repacking, cables replaced and/or brakes/derailleurs cleaned/lubes adjusted, chain cleaned and lubed then $90 would be very reasonable.
How long would it take you to do all of those things?
One of the biggest problems any mechanic has (bicycle/ auto ect...) is that you never really know how much you will have to do to get everything just right until you actually get into whatever you are working on. At least half the time you find "little surprises" that require additional time and/or parts.