Real estate taxes..

There is no one size fits all answer to your question. It is a complicated, byzantine system that takes an idiot savant to understand. (I come by my knowledge as the author of The NY Co-op Bible.) Real estate tax is a function of 2 separate items -- assessed valuaion and tax rate. The valuation is determined for each individual building. It is NOT based on sales prices, but on capitalization of a hypothetical rent roll. Your building's valuation could go up, even though the one next door goes down, and vice versa. In contrast the tax rate is the same for all co-ops and condos city-wide -- currently it's 13.241%. Basically to figure out the amount of real estate tax you multiply the valuation by the rate (this is something of an oversimplification because the transitional not the actual valuation is what counts, but that's for the advanced course.) I invite you to have a look at my website, High Rise Society that has a post on this very topic. Here's the link
http://www.highrisesociety.com/money/what-goes-up-must-come-down-sooner-or-later/