According to the 2009 annual survey by MetLife, the average cost of nursing home care in the Boston area is as follows:
$107,000 (semi-private room)
$119,000 (private room)
The annual costs ranged from a low $91,000 for a semi-private room to a high of $151,000 for a private room. You can see the complete MetLife report (in PDF form) here.