Cheap cheese is tasteless. Can I make it tastier in my mac and cheese?
Cheap cheese is, as others have explained, cheap for a reason.

You should be able to find old/extra old (AKA "sharp"/"extra sharp") cheddar cheese in the cheap section, which makes a reasonably good starting point - this cheese does have some flavour.

Daniel says he simmers the milk; I generally start with evaporated milk, which is even more economical than regular milk and keeps in the pantry forever.  Although I would not use evaporated milk in just any recipe calling for milk, it happens to work quite well for Mac 'n Cheese.

Other common additions to help offset the lack of flavour in poorly-aged cheeses are:


Salt. Remember, salt is essentially a flavour enhancer and will bring out the natural taste of any other ingredient.
Mustard.  Prepared mustard is OK, but concentrated mustard made from dry mustard and a small amount of water is even better, so you can avoid having to add too much liquid.  This doesn't enhance the flavour of the cheese, but it does share some of the "sharpness" associated with cheddar and makes a good complement.  As a bonus, it also acts as a natural emulsifier for the sauce, helping to minimize separation and curdling.
Ground cayenne or red pepper.  Although most people probably don't associate Mac 'n Cheese with piquant, a small amount of this won't make the sauce noticeably spicy, but it will add a bit of the same "kick" you get with very old cheese.


If all else fails, my "secret weapon" for Mac 'n Cheese is - not kidding - the sauce base from Kraft Dinner (AKA Kraft Macaroni and Cheese Dinner for you Yankees), especially if you can get the "extra sharp" version.  This stuff is dirt cheap (often just 99 cents for a package) and before you dismiss this as heresy, keep in mind that the idea is not to use the whole thing.  Just a teaspoon or two to enhance your homemade sauce.  If you don't approve of such shortcuts then you shouldn't be buying cheap cheese in the first place, right?

So there you have it.  Try some or all of the above; I'm sure you'll end up with something that's at least acceptable, if not great.