That's definitely a good example of where things get tricky, but smart contracts are not a dispute resolution mechanism, they're part of a shared infrastructure

That's definitely a good example of where things get tricky, but smart contracts are not a dispute resolution mechanism, they're part of a shared infrastructure. If you use a smart contract you don't need to maintain any sort of backend at all. Your infrastructure costs are basically zero because they're baked into the cost of using the contract, which is paid on every transaction. You also get interoperability for free without having to build out any sort of API layer. Smart contracts are not the solution to all problems but I think they have some really interesting use cases.