It certainly can be, there are different qualities and costs of modular construction. Decide whether you will be doing the contracting or will be hiring someone. You need to compare the costs as opposed to the different quality and choose what is right for you.
It might be, but you should compare the cost of stick built to modular. Talk to a local builder as well as the modular companies. You should also consult a local Realtor who can advise you on the price range and features of homes selling in your area. If for instance, there are other modular homes around you and they have a track record of selling in the price range you have in mind, then this type of construction may make sense.