$12 or $15 at the end of the day are neither of them living wage. It helps, but not a lot.
As for first hand knowledge, I'm just going to share this story. Minimum wage in Australia is A$ 16.87. A couple of years ago, I worked in this small diner, about 10 tables, seat 40 people at most. Open 11 a.m - 10 p.m. It's in a shopping area, but there are plenty of competing businesses there. Usual turnover per day is about $500, doubled that on the weekend, a bit more if we have a function. However, there are a couple of months in the year, most notably after New Year and Easter, that we had no business, the place stay open but we'd make only $300. Barely enough to cover the wage for the cook and waiter/cashier.
I stay a good friend with the owner to this day. You couldn't find a nicer guy, but he couldn't afford more than $13 an hour for his staffs, plus whatever tips we got (not a lot, Aussies don't tip well). All in all, he makes around 60-70k a year out of the place, and actually worked a side job after staying in the kitchen for 10 hours a day. Small businesses have if tough a lot of the time, and while $7.25 is laughably low, I'd imagine if a business in metropolitan Melbourne is that hard to run, one in Kansas or Alaska would have it worse.
Minimum wage jobs should only be treated as a learning experience, aiming at them as something to provide for your family is not something you want.