With the many, many bike carriers available, your first consideration when buying one should be on the functions and features available -- NOT on the price tag!
Consider such things as how many bikes the carrier holds, how it fastens onto your vehicle, where you intend to take bikes using that vehicle and that rack, etc.
It's very important, too, to think about who will be loading the bikes onto the rack or carrier. Smaller people will struggle with a bike carrier that's mounted high on the vehicle. Take such practical matters as that into consideration when you shop for a way to transport your bikes and go biking.
THEN, once you know what you really need in features and functions, you're ready to consider price ranges. Whether you're buying at a local bike shop or department store, from private individuals, or you're buying a bike rack on eBay, you'll find a huge range of prices. If you have a good idea of what you need in a carrier, how you want to use it, and even how often you'll be transporting bikes, you're ready to make the right selection on pricing.
Never buy a bike rack or bike carrier based on price alone. You might not even need such a way to transport your cycles -- in which case, don't waste the money on one. Use the money instead for the best bike you can afford to have the most fun you can biking!