I'm thinking about building one, how much do they cost for all the supplies where should I buy everything? And what should I buy?
In times like this, this is when you use the search bar.
Check out the Build-A-Jib 101 cult, they have everything you need
Just come to Ski Ward's in central MA. Take a look: https://www.youtube.com/watch?v=BdF0KcrRdZw&index=1&list=PL327AE523D65C94A0. There's an AirBag, too!
I used about 15 10ft 2x4s, 3 one inch diameter 10ft PVC pipes, 2 sheets of plywood, a shit ton of 2.5 inch screws and 2 inch screws for the rail, and we used concrete for the foundation of the ramp part of it.
Mine costed about 100 bucks because my dad already had a lot of the materials from his company. Lowes and Home Depot will have everything you need. If you're parents or family have a construction company like mine, they may go to a builder supply and they generally sell things cheaper to long time buyers so you could get some deals on wood/ plywood.
It took me like a week and a half but could be done in a day or two if you devote the whole day to it and you have everything you need to do it.
You could definitely find better instructions in that cult than I could give but if you wanna know how I did mine pm me or something.