I don't have numbers to back this up, but I strongly suspect your average hotdog cart sells more hotdogs per day than your average indie or solo game developer sells iPhone games per day.
A new street food vendor only competes with other food vendors in the area. A new game developer competes globally, against both established studios and hobbyists happy to work for free because it's fun. You have people who want to make games so badly they'll fight to get in, knowing fully it's low pay and long hours.
Any way you look at it, the reason game developer salaries are relatively low is because supply for the jobs is higher than the demand.
It's a bit silly to compare the two because the economics are so different (local, non-scalable product vs. global product with zero marginal cost), but I stand by my assertion that there's no inherent reason why game developers should earn more, on average, than food vendors.
Inherent reason to me would be that the skills of food vendors are more common and easily acquired than those of game developers. I have a BSc in CS and over 10 years experience. This guy learned to make bread from his girlfriend and opened a stand shortly after. You're probably unfamiliar with the game industry beyond popular articles and headlines, but I can assure you tha demand for qualified engineers is very high. At least in the parts of the industry that are profitable. i.e not the millions of bedroom coders or cheap labour that pump out mediocre games.
I guess we're talking about different things - you're talking about the high end positions, I'm talking about the average case. To get my analogies even further muddled up, you're talking about musicians signed with a major label, I'm talking about all musicians, from rockstars to people busking in subway stations. The expected value is going to be very different if you're only taking the top N percentile.
(not particularly relevant, but I have friends with similar qualifications and experience as you who work / worked in the industry at... shall we say more mediocre studios. I suspect their perspective on this topic is somewhat different from yours.)
A new street food vendor only competes with other food vendors in the area. A new game developer competes globally, against both established studios and hobbyists happy to work for free because it's fun. You have people who want to make games so badly they'll fight to get in, knowing fully it's low pay and long hours.
Any way you look at it, the reason game developer salaries are relatively low is because supply for the jobs is higher than the demand.
It's a bit silly to compare the two because the economics are so different (local, non-scalable product vs. global product with zero marginal cost), but I stand by my assertion that there's no inherent reason why game developers should earn more, on average, than food vendors.