L'Espalier is a possibility, as we have nothing for the rest of the day, but it's quite a commitment, time- and price-wise.
Eastern Standard Kitchen is a possibility, for sure.
But since we're footloose and fancy-free after our meeting, we can go anywhere that's more or less easily accessible by cab or transit. So... best non-break-the-bank lunch on a rare visit to Boston?
In that area you are best trying one of the small ethnic restaurants because it is a wasteland of restaurant chains.
Pho Basil on Mass Ave
Chili Duck across from the Prudential Center
Cafe Jaffa on Gloucester Street between Newbury and Boylston.
Mei Tei Noodle Cafe on Hereford Street
Trident Booksellers Cafe on Newbury.
Le Voile on Newbury.
I think they are all open for lunch.