I guess the first thing you should know about Marina Bay is that it is a neighborhood not, as the other answers below imply a single condominium complex. There are currently 11 existing HOA's in the neighborhood with one additional live/work space under construction and at least two additional single family home developments being proposed. HOA fees in the neighborhood range from under $100 a month to over $500 a month and they also vary by what they cover in terms of expenses and maintenance.
The Marina Bay area features lots of bay front land and nature while also having several parks and the Bay Trail running right along the Bay for well over a mile. If you have other questions regarding the area feel free to post them here or contact me directly.
The cost is also a loss of freedom - to be penned in like a caged animal. Plus the loss of expression as a free american so you don't get to touch the building, you don't get to have great architecture. You just get to perceive you are safe. But it is a place they walled off and pretended it wasn't Richmond. Don't mind the cameras either. You'll never get it.
It depends on the size and location of the unit but generally speaking they are anywhere from about $275-360 per month. Right now it's a bit tricky to purchase there because of pending litigation but feel free to contact me for more information.
Better Homes and Gardens | Mason-McDuffie Real Estate
2095 Rose Street, Suite 100
Berkeley, CA 94709
DRE # 01902004