There's the Buckminster (~90$) and the Howard Johnson (~110$)... but they are POORLY rated on Trip Advisor (and I mean VERY POORLY rated).
I ended up booking three nights at the Midtown Hotel, which is a bit more expensive (140$) and a bit further (1 mile) from the Avalon... but seems a lot better.
Every other hotels in the area were too expensive for me.
I'm not from Boston though.
If you're booking the Midtown too, It would be nice to have a "walking buddy" on the way home... since I'm by myself and will probably have a few drinks in a city I don't know
Hope that helps!