Some properties are part of condominiums undergoing 40 year re-certification - which usually means a special assessment, dirt, noise, and overall unattractive (at the moment) look of the building.
Other condos have large maintenance fees - so the price is lower to compensate for the maintenance fee. Some other properties are distressed sales (foreclosures or short sales) - with prices lower than the market - which attracts many buyers and creates bidding wars.
Hope this helps,
Beachfront Realty, Inc.
There are pros and cons to most of Miami's neighborhoods, and it probably makes sense to talk to an agent, and get a better feel for exactly what you want and need.