there is something just plain wrong about a small business making less than $5000 being required to insure for $5000
I think you have it wrong. Since the insurance cost is $5,000, your business must be able to generate revenue in the 80K neighborhood before you can seriously consider renting the booth.
Regulators don't care about your problems. If you can't afford to pay the man, you can't play.
A good lesson.