Do you mean a life-time $50k? Otherwise an annual deductible of $50k sounds ludicrous. Maybe if they tied it to yearly income, it would make more sense.
Dental "insurance" is basically a savings plan with a negative return, considering the low lifetime maximums, and the fact that biannual cleanings aren't that expensive out of pocket. I have a $20k deductible (with lower premiums), and I'm coming out ahead. There's societal side benefit that paying with your own money makes you a more discriminating consumer.
The $50K is not outrageous, assuming you have the savings to cover it. You need insurance for the big things, which is basically anything more than a two-day stay in a hospital. The costs blow up from there.