somewhere between $50 and $5000 depending on about 2 million different options of radio/gyro/engine/fuel/tools/servos/upgrades etc etc etc.

on the budget side, maybe about $800-$1000, but would expect to pay $1000 to $1500 for reasonably good gear as mentioned above. Talk to your hobby shop and get a complete package put together, they usually give a good discount with a mass purchase/starter kit.