It is still useful to ask the question just so we know the answer. I admit the person asking in this case probably didn't mean it this way... :)
On speed limits, when it comes to road deaths, you get people saying "one death is too many" and so on when one of their loved ones die, even when speed limits are set to 20 mph.
These people are wrong. Asking why a 1 mph limit is bad can help reveal that we do put a cost measured in lives on convenience, and we do face the risk of death when driving a car, and everyone has a number they think is reasonable.
Asking why $100/hr is too high can at least help us decide on a quantitative way to decide on a number rather than just guessing.
Another reply already addresses your question about speed limits, which is another great example through which to examine these questions.
"Reasonable" is a completely subjective standard and not a good way to run a complex economy with an infinite combination of job seekers and providers.
Who gets to decide what is reasonable has big real world implications for millions of people. Get it wrong, and as we see in California here, people lose their jobs and businesses close all because some politician or bureaucrat (or misinformed voter) thinks they know better than workers and employers what the correct price for labor should be.
Because you intentionally picked large unreasonable number and now want to argue it implies much smaller number is reasonable.
If maximum speed of 50km/h is reasonable in cities, why not making it 5km/h?