The only way to do it cheaper and end up with it potentially being right is to do the job yourself. Working on these cars is no easy task and to pay someone to do it right is going to cost some coin.
That being said my car sits around 700whp now with the stock LT1 motor, 11psi of boost, fuel System and E60 fuel. Been this way since 2019 and haven't had any issues. The Ethanol fuel is what is allowing this to happen.
Since you do not have E85, you need to get dynamic compression down. Ideally lower compression pistons would be best. However, a cam swap will lower dynamic and allow you to hit 700whp on 94 octane with 10-11psi of boost. You will need the LT4 fuel system. Jenetty Racing offers a
Super Street Brawler package that achieves this.
The thing for me is, If you are going to spend 20k for the entire package, what is another 3-4k or so for rods/pistons installed while it's apart. The engine will already be torn down to the short block regardless. Then you have the bottom end to support another 200+ whp reliably if you desire to turn it up vs being pretty much limited to around 700whp with that package. Either way I know Jenetty has done a lot of these packages and had no issues with reliability.