How cheap will ethereum gas fees become after eth2? I am asking for the technical explanation that would help understand how the fees will go down and to what level they might reach.
Transaction fees on blockchains, including Ethereum, are put simply, based on the supply and demand for the blockchain.
On the supply side, How many transactions (TPS) can Ethereum 2.0 process? indicates that rollups can process 100,000 transactions per second (TPS), and that eth2 will have ~1000-5000 TPS.
The demand side is much more difficult to gauge. The transaction fees on eth2 will depend on how many transactions are done on the main, "Layer 1", Ethereum chain itself, and how many will be done on "Layer 2" rollups.