> On what planet is a loss of 70% of the resources to the matching process between buyers and sellers "incredibly efficient"?

One where the market maker is taking up the cost of providing a market. E.g. Steam takes a 30% cut for providing the infrastructure required to distribute games. Some people/companies can do it for less but it is the best option for a majority of sellers.

If the market maker did not the seller would get more revenue but would also eat the cost directly instead of paying someone else to do it.