Not entirely sure what this has to do with reloading, but I don't see an issue with it once in a while...
When I build a bench rifle, it's $5,000 worth of time in the machine shop alone.
That doesn't usually include base parts price.
'Rail' guns start about $15,000 and go up from there QUICKLY.
If you are looking into a more common rifle fired from bags,
It's pretty easy (and cost effective) to get 10 round .223 groups you can cover with a dime (10 cents).
That's mostly matching bullet weight/velocity to the barrel rifling twist rate you are using, and getting the chamber in the correct shape, and the chamber located correctly in front of the bolt.
It's the same for bolt or auto loaders, bolt face square to the chamber/bore,
Barrel bore square to the front of the reciever,
Reciever bore aligned with barrel bore,
Bolt locking up solidly on all lugs so the bolt face STAYS square during the chambering/firing process.
After the mechanics are 'Right',
Then it's up to internal ballistics, external ballistics...
(Terminal ballistics don't much matter when punching paper)
It would help to know application.
We talking factory trim, modified with weight limits, unlimited, outlaw, rail guns...?