~snip~
You have a point but from my understanding and thinking, rate will be the last thing someone who is about to loose everything. Instead of the service charge, what client will be more interested in is the integrity and reputation of the service provider. People have lost fortune because of going for cheap prices and that is one thing scammers use to lure their customers. So any service provider that is able to build reputation will control a large share of the market.
Rate has been one of the problem with companies that render this kind of service and clients. Since not all wallet recovery services are scam, the genuine ones especially the ones that has reputations may want to be collect high fee due to how honest their service could be and based on marketing expenses.
Some would give a bonus to referrals indirectly increasing the fee. People are losing fortune to scammers and that alone is making people to be wise these days to do some research before giving their wallet information to unknown people online in the name of wallet recovery.