The costs to make a burger at McDonald's include property taxes/rent, food costs, utilities, other things, and labor. Labor is only one part of it. If a burger costs $1, and labor is 50% (very generous estimate), and minimum wage doubles, the burger now costs $1.50. Now at the end of a 4 hour shift the employee now has, say minimum wage rose from $7 to $14, $56 instead of $28. If they were going to spend that all on burgers, they used to be able to buy 28/1=28 burgers, while now they can buy 56/1.5=37 burgers.
So even with extreme examples, the minimum wage worker comes out ahead here. People who made more before can buy a bit less now but it's not as drastic as it's made out to be.
Beyond this hypothetical, here's a study that says rising wages to $15 would only increase prices by 4%. https://www.marketwatch.com/story/raising-fast-food-hourly-w...