Not only that but as a chef you presumably have to make it perfectly every time. I remember reading Jacques Pepin saying how he doesn't get bored of cooking because it's never the same: even if you cook the salmon 50 times, no two pieces of salmon are identical but a good chef should be able to make them all taste very nearly the same.
On the other hand, I imagine that chefs have a much more nuanced palate than the regular person so I wonder at what point are most normal people unable to distinguish the differences.
If you have reached a high level of cooking then I apologize and will admit I'm wrong, but it seems wrong of us, who haven't been through the same process, to say it's easy. I'm sure people who aren't programmers might wonder why software always has bugs and security vulnerabilities and think it shouldn't be too hard to write programs without them.
The problem with this sort of discussion is that everyone thinks they are worth more than the market will pay, and that the market is somehow broken.
http://sweets.seriouseats.com/2013/08/how-many-eggs-should-i...
If the restaurant is high-end, the icecream should have the correct ingredients to pair with the other food.
Pastry making is often compared to an art... but then art doesn't pay much either.
I do agree with your overall point that chef's skills probably aren't specialized or difficult enough to command high wages in the long term.
This is an example of pastry chefs overvaluing their own skills, so not surprising there is labor substitution happening.