Help for Tonight - Lexington, Burlington
Many fewer options that there should be in Lex/Burlington given how many people work on 128 ... if we define 'expensive' as the Capital Grill, I'd recommend Pappa Razzi. Yes, a bit of a chain (as is the Cap Grille), and no - you will not grow cuisine-wise, but I think it's a good value with passable food and atmosphere.
Lemon Tree on the great road for ok Thai/sushi
Naked Fish - further up for eclectic whatchamacallit
The food court at the Burlington Mall (esp the indian food)
are some of the cheap eats in the area which serve acceptable food and will not break anyones bank. There is an Indian restaurant in Lexington center called Kushbu which serves excellent Indian for a good price (but you will have to watch your pocketbook with what you order) - and it has a good looking dining room.