There are many factors that impact the assessments of a building - age, ammenities, maintenance, reserves, updates, remodeling, and location among other factors. If you are looking in the Gold Coast area - the dues may appear higher than most areas due to the fact that this area along with other areas near the Loop offer some of the best building ammenities relative to other condo units in other parts of the city and suburbs. In many building in the Gold Coast and surrounding areas, you have 24 hour doormen or some front desk staff for the majority of the day. In addition, there may be a pool, large workout rooms, common area party rooms, cable (may be included), etc... There are many reasons. However, if you are looking for lower dues - you may want to consider buildings that don't have door staff or many ammenities, this will cut down on the dues.
If you are looking to buy in the Gold Coast, please let me know. I have helped many buyers and sellers throughout the state of Illinois and specifically in the Chicago area. Feel free to call me, if you are currently not working exclusively with an agent, I would be glad to represent you as your buyer's agent.
I hope the response to your question helps.
Licensed IL Real Estate Broker
Century 21 SGR