how many $100 spins in 5,000? $10,000?

If you mean how many $100 spins does $5,000 buy, the answer is simple:

$5,000 / $100 = 50 spins.

If you mean anything else, you have to give the criteria that will determine when you will stop spinning. 

If you mean on average how many spins can you get before losing so much that will will not have enough to perform another $100 spin, the answer depends upon the return percentage of the machine. If the machine returns an average of 95% of the amount bet that would mean that on average you lose $5 per spin. Once you have lost more than $4,900 you will not have enough for another spin. 

$4,900 / $5 = 980 spins on average before running out of money.

The only time I took cash to play $100 slot machines there was a bank of ten machines. I decided to play a maximum of three spins per machine but would stop playing a machine if I had a winner before three spins. Using those criteria I got about 17 spins.