The components for the drone I used here were all together maybe 400 USD. But then you need a controller (Taranis ~ 200 USD), video goggles (Fatshark 300-500 USD), plenty of batteries (20-25 USD each), HD cam (100 - 300 USD), battery charger (50-200 USD). If you want to fly far away or behind obstacles you'll want a long range radio system (TBS Crossfire 250 USD).
The flight time of a miniquad like this is 4-7 minutes, depending on your flight style and the battery you're using. This short time frame is limiting your range, so if you want your drone also to fly back then you can expect to get ranges of 2 km, maybe even 3. If you want to fly long range you can do so with a plane or a flying wing. These have flight times up to 90 minutes, depending on the setup.