Rebuilding an engine for a vehicle can be done by yourself with some time and knowledge and is not that hard.
The cost of the rebuild kit for the engine rebuild depends on the engine you're rebuilding but most engine rebuild kits cost between $300.00 to $600.00 depending on the engine.
For example I rebuilt a 350 small block Chevy engine for one of my old Chevy Trucks and the engine rebuild kit cost me $300.00 which was a reasonable price.
The kit included everything needed to completely rebuild the engine to like new.
You can buy already rebuilt engines for around $1,000.00 to $1,500.00 or even $2,000.00 depending on the vehicle.
Rebuilding an engine is not all that hard but if you don't know how to rebuild the engine it would be best to study up on it or have someone rebuild the engine for you.
Watching some videos on Youtube on how to rebuild your engine can help you learn.