To put it another way - The disabled person gets £58 a week mobility allowance (yes, from the taxpayer, like other benefits)-
John Smith spends his allowance on a taxi to Tesco and back once a week, a Sunday visit to his aughter, and various trips to the doctor, the garden centre, and the cinema.
Jean Brown spends hers on renting a small car from a motability scheme. She pays it to the local private car hire firm that owns the cars. A small car is enough for her, because she can get in and out of it, and she doesn't put a wheelchair in the boot.
Rose White spends hers on a car with a bigger boot that can take her wheelchair, and a door that iopens wide for hr to get in and out. It also has room for her four grandchildren to come with her. For that she pays extra to the rental company FROM HER OWN MONEY.
The price of the rental to the taxpayer for each of these people (by way of the allowance to the disabled person of £58 which they hand over) is £58 a week for each of them, whatever the size of the car. That is about £3000 a year.
I don't know what renting a car costs ablebodied people, because I have never tried it, but it sounds pretty reasonavble to me. The hire companies do it because they get an assured rental, and they get the car back at the end of the three years to sell or rent out again. They don't need to swindle anyone.