There isn’t really a right answer for this. It all depends on how much value you’re giving the bike and the sport of mountain biking in general. But keep in mind, in most cases, you will get what you pay for. So if you’re going to be reluctant to pay more than $500 for a bike, you will end up with an inferior quality model, which may break down quickly with time, causing you to do frequent repairs. This may even cost you higher than the price of a good bike in the long run. On the other hand, if you choose to invest the money, and consequently the time into a high-quality bike, you’ll find that the investment will become gratifying with time. The more you use your bike, the more pleased you’ll be. But don’t also forget that you’ll have to keep the costs of the helmet, pedals, shock pump, and other kinds of gear in consideration.