This tech has been developed several times but ultimately CDNs are now so cheap that P2P is pointless. You can't ignore development cost since it dominates all other costs in this case.
If CDNs are so cheap, why is YouTube insistent that they should get paid for their bandwidth? I already pay for my bandwidth and am quite happy to use it for something like YouTube.
The real reason is centralised architecture gives them control and ability to extract rent.
> why is YouTube insistent that they should get paid for their bandwidth?
What are you talking about?
YouTube has a lot more costs than bandwidth. And a lot of ads and Premium revenue goes to creators.