Some of the comments in here make me really rather annoyed (although some of the others pleasently surprise me by being reasonable).
A 40k car costs the "taxpayer" no more under Motorbility than a £10k car, as you pay the same monthly fee (usually all your DLA mobility allowance) AND a hefty upfront fee to cover the depreciation of the car over 3 years above the level that the DLA payments would cover.
A £10k car might have Zero upfront fee, but a £40k one might have £5-10k - IIRC under the current rules the Motorbility scheme has actually been running at a slight but noticeable profit.
Also Motorbility are a huge fleet hire, they get big discounts on the cars under the scheme, so will usually pay a fair bit less than any individual would to get the cars (they have a hefty discount on the RRP), so the "£40k car" is probably closer to £30 or £35k, and the scheme normally ends up with getting a slight profit at the end of it.
The change has been made mainly for the sake of the DM and image and uneducated idiots who can't ever be bothered to look into the truth.
A £15k car for example probably won't be suitable for many people (why stop at £15k, you can get a Picanto for £6 or £7k), as one of the things that people who take the motorbity option often require is a dealership near enough to them that the car can be serviced with minimal inconvenience, or may need an Automatic (usually costs a bit more), or a larger vehicle to enable them to get in and out comfortably.
It's surprising how important an extra few inches in height to the seat can suddenly become when you' have say a hip problem, or how important a higher cabin area can be if you can't bend easily/without pain, let alone little things like the height and position of the boot opening, or the size of the boot (things that are really quite important considerations if you've got a wheelchair, especially if the person who pushes it may be a little older, or smaller), and those are all before the normal considerations of things like how comfortable is the driving position for you, or can you see around comfortably from the drivers seat (the pillars in some cars are really badly placed for people of some heights)
Also the 5 mile ruling is going to make a lot of problems for people who may drive the car themselves when going around the town, but have a family member nominated to help them when it comes to longer drives or things like hospital visits (IIRC under motorbility only the nominated drivers, or the staff of the servicing garage etc can ever drive the car).
It's unfortunately the Motorbility scheme throwing the baby out of the bathwater in an attempt to appease the DM readers who can't or won't be happy until the only choice for motorbility cars is a nice little orange plastic three wheeled thing that only takes the disabled person.
There are problems with the old scheme, but it would probably have cost less to have dealt with them - the changes in the rules now aren't likely to stop someone from lying about where they live, and a lot of the people that abused the scheme lived in the same town (or even same house) as the person who the car was for the use of.