I don't need an explanation and no one needs to build a sustainable business because any of the many AR barrel manufacturers could cut Savage pre-fit barrels on the same tooling they use for AR barrels.
And that is precisely why you misunderstand this so much.
There is no incentive for a current company to offer this. They can make a larger profit by keeping their current tooling arrangement (there's a fairly significant time investment in creating new toolpaths that you seem to be ignoring) because they know the items will sell and they make profits.
They will need to use different barrel blanks for a Savage pre-fit than an AR-15 barrel blank. You will need to find a new method of fixturing since mass manufacturing doesn't generally use standard chuck jaws on their lathes because they have automatic stock feed capabilities. You will have to train workers to run the machines for the different barrels. You will have to find new suppliers for your barrel blanks, but you will not receive the same volume discount. You will need to pay to market the new product so people hear about it.
I say this all as someone who only owns rifle builds with Savage-style barrels. I have a Cabella's special Savage (12FV) and a Nucleus on the way. I would buy a cheap barrel like that to give it a shot, I'm just trying to help you see why it's impractical currently for companies to offer this product because so few people want it and it isn't as simple as you make it out to be.
Criterion's pre-fit Savage barrels are more expensive than the AR barrels because they need to maintain a higher standard of accuracy and because they sell FAR more of them than they do of their Savage barrels. When you sell more, costs per barrel go down because you get bulk discounts and you can build greater efficiency into the process (you don't have to worry about whether or not you'll recoup the cost as much, because you sell a lot).
AR barrels also require significantly less quality control and precision than a barrel for a bolt gun. If the bolt gun barrel shoots 1 MOA people will be disappointed that's all it can do. If an AR barrel shoot 1 MOA people will be quite happy with it.
Again, I've been over these issues but you seem to be ignoring literally everything I have taken the time to try and explain to you. You're free to believe there's a market for it if you'd like and contact the companies yourself, but I don't think you'll get the response you're looking for.