Mitchell is the Guitar Center house brand, named after the founder Wayne Mitchell, and obviously sold only at Guitar Center. They buy instruments from manufacturers in Asia and put their brand name on them. They're not necessarily bad instruments, but they're not necessarily good instruments, either. The quality varies widely from guitar to guitar, so make sure you know what you're getting if you buy one. They will never be collector's items or have much resale value (unless you become a rock star), and in fact you might have a hard time a year or two later even
finding another of the same model.
Personally I think you'd be better off with a low-end Yamaha or Ibanez. These are real basses designed and made by real companies that have a genuine interest in your satisfaction because they are going to want to sell you your next bass and the one after that. There's likely to be a variety of exact matching accessories (pickups, tuners, pickguards) available for your bass from both the manufacturer and third parties. There's
quite a selection of these instruments in the $200 - $300 range.
But if you are in love with that Mitchell bass, I can assure you Guitar Center was making money at $250. Go in and play it for a while, sometime near the last day of the month, and then politely tell them you're sorry you missed the sale but your budget is only $250 and offer them that much, cash
right now. You might be surprised.