I don't know where that quotation comes from, because you didn't cite your source... but it looks to me like they are calculating the numbers as though you can isolate a certain group of workers and products as though they exist in a vacuum. Doubling wages in one sector, especially a sector as large as food preparation and service, is going to result in significant inflationary pressures in all other sectors. There would be a major rush into these sectors by employees, meaning that now you need to also raise the wages of, say laborers in the trades. So now the actual physical plant goes up in price, and that raises the price of your Big Mac meal, as well.
Also, the study seems to use MacDonalds as a model. That's an insane example to use. A large percentage of businesses don't even turn a profit, at all. Over half of them fail within 3 years. I owned a cafe. A general rule in the food service industry is that the cost of labour should be around 30% of your total costs. Most restaurants are in a constant struggle just to break even. Now you're going to double my labour costs, make them 60% of my total costs, and I'm going to raise my prices by 5% and that's going to take care of everything? Bullshit.
Do the math, yourself.
A restaurant that does $2,000,000 per year (which is a pretty modest revenue total), pays around $600,000 in wages. Then you have another $200,000 (10%) or so for rent/mortgage. Then another $600,000 (30%) in food costs. Then you're going to need to service and upgrade your equipment and furniture and space, which is going to be another $80,000 or so (4%), and you'll need a POS processor and book keeping and banking services at another $60,000 (3%), and then utilities and garbage removal and snow removal at another $60,000 (3%). Then you're going to need to do some marketing which will run you $40,000 (2%) if you're a great restaurant that can get by on word of mouth and a low marketing budget. And then you have a whole lot of miscellaneous costs from insurance to cleaning supplies to toilet paper at $60,000 (3%) if we're conservative. And that leaves me with $300,000 if I'm really, really careful, and pinching pennies. And from that I put $200,000 toward paying down my original investment for the first 10 years or so, if I'm disciplined.
And I'm left with $100,000, or 5% profit... which is good for the restaurant business. Really good.
But I'm going to double my payroll, to put myself $500,000 in the hole in the budget laid out above (not to mention the increase in my food costs as every employee down the chain is getting a raise that doubles their wage as well), and then I'll just make that up by charging you an extra $0.19 for your burger.
You people are drunk.