I was basing it on the other meals, which were on the order of $11-13. A Big Mac meal isn’t $5.99 where I live so the gap feels larger to me.
Either way, I think that the assertion of “this thing worked over there so it will work the same way here” is overly optimistic. But ultimately I don’t much care - I rarely eat there, so if McDonald’s got very expensive or went out of business, it wouldn’t have much impact on my life. If they want to unionize, more power to them.
I’m not a fan of unions overall. I recognize that they’ve done some good things, but the people I’ve known who were in unions or worked in union shops don’t describe places that I’d want to work in.
The cost for this meal appears to be US$5.99 in the US - quite similar.
That's not close to $15 (or $20) by any stretch of the imagination.