Interesting. But how would you recover a wallet without having any access to the keys, phrases or other sensitive data? That is technically impossible. If that data is provided and the wallet is recovered, then you would have access to all the funds in it. Upfront payment doesn't make sense because after recovering a wallet, you will directly have access to the funds.
In most cases you can use a publicly available open source script to extract a hash string from the wallet file directly. The original password can be derived from this hash without revealing any information about the wallet.
The only exception I can think of is the recovery of part of a bip39 or similar passphrase, this would allow direct access to funds.