Both my horses are what I guess you would consider "grade" - I don't have Monty's papers and he is still registered in his breeder's name, she won't transfer ownership. He is registered, and I could obtain photocopies of his papers, but the real thing would be nice. My filly isn't registered anywhere and I don't know if she can be. I don't care, though I did manage to pick them both up quite cheap for the quality they are (and the education Monty has). Here, registered horses sell for more because of bragging rights. That thar horsey is a registered whatever, that means it MUST be better than an unregistered horse. The exception to that is TB's and Standardbreds, because they are a dime a dozen and the majority aren't very good quality.
That said, a young, educated horse with proven results in the show ring is worth money whether it's registered or not.