Aquafresh Is Good & Cheap!
I can usually find Aquafresh on sale for a dollar a tube during occasional sales at our local supermarkets. Generally, Aquafresh or Colgate Cavity Prevention (basic white paste) can be found for a buck a tube; I stock up when a sale is on. But if neither is on sale, I buy Pepsodent Complete, which runs around 88 cents a tube at Wal-Mart and is a good cleaner with a pleasant taste.
My dentist told me I can use just about any fluoride toothpaste, but I lean toward Aquafresh and Colgate CP because they have the ADA seal. Those and a rinse with Equate Spring Mint Antiseptic (a Listerine clone with the ADA seal) and a good flossing helps keeps my teeth in good shape--along with my dentist, of course!