Cost isn’t the issue with recovering wallets with small amounts because the team already said, they would consider recovering wallets with small amount as a favour but I think they charge a 20% for recovery which is fair to me but I think these fee should be paid after the wallet have been recovered and not upfront.
Do you think anybody would pay for wallet recovery service before the fund in the wallet can be recovered? I don't think so and it's only someone that is not sincere will want to get paid upfront before a wallet can be recovered.
I have seen cases of people that looks like scammers asking for upfront before they could work on wallet recovery cases. I believe if fund is inside the wallet, after recovering the fund in the wallet, the percentage agreed rate can be withdrawn after the job is done.