The only way to fix this is you have to build a new cloud that has lower networking costs and force the existing competitors to lower their prices.
One of the real problems is that cloud providers can just waive cross-AZ traffic for their own managed services but charge a lot for cloud customers.
That is why no matter how smart your software is they'll always have the upper hand and build things better themselves (why everybody using the BSL license).
It’s like owning the entire supply chain. I remember this bit from someone who used to work at Heroku. It’s impossible for us to switch we spent so much time making the system work with AWS, switching or adding another provider would be a kin to starting over.
Suffer and try to vote with your wallet (example oracle cloud has lower bandwidth pricing).