You can get affordable maternity clothes, but they do not last for subsequent pregnancies. I had some hand me downs that are the same label that have gone through about 5 moms that lasted 100 times better through my second pregnancy in 2006 than anything I bought new in 2004.
They also have the worst return policy in the world. Do not try to buy anything for later on in your pregnancy as you are stuck with it if it doesn't fit.
I will say that their staff are generally very helpful and there are numerous locations. They have a good mix of things you need and it is affordable.