The answer depends on your financial condition and how much you value cycling.
People nowadays grumble about the high cost of cycling, and they have a reason, with good bikes costing $10,000 or more. Those top-shelf bikes are magnificent works of engineering and technology, but they are not required to enjoy the sport. In fact, the R&D that goes into the halo motorcycles helps the typical consumer. While a top-of-the-line bike in 1991 would have cost $2,000, today’s components, suspension, wheels, and overall package considerably outperform those from 1991.
We suggest hardtails for $1,500 and full suspension for $2,000-2,500. You can acquire bikes for less money if you avoid name brands or accept substandard parts. But you’ll wind up spending more since those bikes will fail, need components sooner, or be so miserable to ride that you’ll upgrade anyhow.
On the other hand, how much is too much? Clearly, the answer depends on your financial circumstances and how much you value cycling. If you ride your bike for hours, the elegance and comfort you get for $10,000 may not seem so great. For between $4,500 and $6,000, you can buy great bicycles that are only little heavier or surpassed by the stratospheric top end.
If you’re buying a new off-road bike, budget at least $800. (in the US). This is the pricing threshold where decent hardtails with useful suspension forks start to appear.
A $4–500 bike is more than competent for street cycling, but heavy.
Consider a comparably priced hybrid for street riding. No advantage to big tires on the street, and your gearing will be better for the hybrid. Plus, for $5–600, you can get a lot of hybrid. Avoid the suspension fork. They’re pointless and heavy at that price.
If you want an off-road bike, go for a 2×9 or 2×10 drivetrain with hydraulic brakes. Of course. It will cost roughly 800 dollars and possibly 11 or 1200 dollars.
Buying used is cheaper. Many bikes sit idle across the country. Find one that fits and is suitable for your riding style. Bike replacements are available for beater/commuter/car bikes.