A tiny minority of quilters own long arms. Most of us would not want to invest the price of a car and a whole room of our house for something like that. Many who do own them think of them as business investments, and maybe get small business loans to help pay for them. After you're good at it and can do quilting for others, the machine might eventually pay for itself, and as a home based business, the overhead would be minimal. It would allow the owner to stay at home, set his/her own hours and have this marvelous machine for quilting not just other people's tops but some of your own. If you can quilt on a domestic machine, you can probably do it better on a LA, once you've learned the basics.
On the other hand, a person like myself with a long history of dabbling in various crafts would be insane to buy something that expensive. It would feel like a ball and chain to be that ($$$) committed to quilting, even if I love it at the moment.
If you're considering such a plan, first try it either at a local shop or at a quilt show, where there are often several different machines to test drive. You might surprise yourself.