So you're moving on up, to the eastside deluxe apartment in the sky? You finally got a piece of the pie and they want to charge you 1k a month!!
The one's I've seen have nice Public elevators, heated pools, a movie room, sauna, outdoor Jacuzzi, Door Man, Concierge, and etc. $1K still seems high to me though but the prices might've gone up from when I entertained the thought of moving into a condo.
Most of the assessment/HOA/maintenance fees goes toward the reserve fund for the building. The building will dip into the reserve fund for big expensive renovation & maintenance projects (eg, renovating the roof requires helicopters to lift some of the materials, a major whole building outside facade repair can take months, renovating the lobby, elevator modernization etc). The rest are for the amenities: doormen, pool, on-site maintenance people, maintenance for the common areas & depending on the building centralized heating & cooling + hot & cold water + sewage + cable & internet)
And some just don't have enough tenants, so the fee is spread out over far fewer residents. 2016 Main is a prime example.