LA quilting is getting more expensive to get done all the time.... $.015/sq inch for just pantos and that figures out to around $200 per queen quilt....so I have been doing my own on my Janome 6600. I am not even close to being good at it, but I keep plugging away at it. My brain simply cannot make the conversion from moving the "pencil on paper" to moving the "paper under the pencil". So one day I will have the space and $$$ for a LA.
To be able to justify the cost, you would have to take the cost of a LA monthly payments and determine if you spend more than that to outsource your quilting. So if you regularly spend $250 monthly for LA quilting and the monthly payments are $200 then I would say yes, the cost is justified. If you only send out a quilt every couple months or so, then you probably can't justify the cost.
Bottom line - if you have to be able to justify the cost to feel good about buying one, you probably shouldn't as you will always feel obligated to hurry. Then it becomes more of a job and less of a hobby to enjoy.