Does a tx fee on a Smart Rollup call the same as a Smart Contract call? If yes, that means every popular Dapp in Tezos will want to run on Smart Rollup so they can charge tx fees and keep it to themselves they just need to solve the token withdrawal time issue.
Does a tx fee on a Smart Rollup call the same as a Smart Contract call?
tl;dr - you can implement whatever fee model you want for your rollup.
Fundamentally, someone is going to have to pay some L1 fees to include a message in the shared rollup inbox. Likely this message will need to include a signature, proving it's from a specific user.
But the user providing the signature need not be the one paying the L1 fees. You could have other schemes, where the users pays a fee on the L2 in some alternate token (though CTez is probably the right "default token"). Additionally, if you have tons of money because you're e.g. ManU, you could just pay the fees yourself as user acquisition and operating costs, and rely on a different price model to make up for it (more like Web2).
they just need to solve the token withdrawal time issue.
tl;dr - withdrawal times are likely solvable in practice if you make trade-offs.
There's no way to have fast withdraws with the same rigorous security guarantees SORU provides out of the box (namely, single honest operator can defend against any number of malicious operators). That said, there are lots of other options rollups can implement in practice. We're discussing a bunch of them, and I think the way forward is to have lots of rollups trying different things. The cool thing about SORU is that it provides a very secure, scalable base on top of which you can build lots of different things.