These prices don't sound outrageous. The greater Boston area is one of the most expensive regions in the country. Will the prices continue to drop is anybody's guess. Allegedly the prices have been falling for the last 3 years so there is the chance this is the worst of it or we could see another year.
The way to make the decision is to look at Belmont specifically and not focus too much on the national real estate market trends. Remember real estate is hyper local (each individual area is affected differently by market crisis'). Positives are that Belmont is a stable high-end market (meaning it isn't currently going through a gentrification of sorts - i.e arlington, south end, etc). The area has great school systems and is very close to Boston.
Also look at the facts ...
Condo market snapshot:
Last year, 64 properties, 114 days on market and median home price of $427,000
This year, 41 properties, 165 days on market and median home price of $479,000
Summary: Less inventory higher prices which means the condo market in belmont is still strong despite general market slow down.
I hope that helps. Good luck!