People, especially businesses would spend $30-$40k on a car, which loses value as soon as you drive it out of the showroom. It will never breed, and when it comes time to sell you will probably get bugger all for it. Whereas if a proven pair of GTP breeders, should produce offspring and unless there is a flood of them on the market, will be very valuable and you will be able to recover your initial outlay in the first few seasons. You will still have the original pair, although a few years older and maybe needing a seasons break, which again unless there is a flood of them, would still be worth a nice sum. Of course you could always keep some of the ones you breed as future breeders
On the down side if they do not breed, or one dies then you have probably blown a large part of your $40k. Unlike a car you cannot insure them.
It all comes down to perspective. If you have enough money to be able to stand to lose $40k if things do go wrong, and there are people out there (not me) that can, then $40k would seem reasonable looking at the potential. It is probably more suited to a commerial venture, or maybe a group of people that can form a joint venture to spread the risk, rather than just one individual.