From what I have found ... with 0.3% increasing the value on the Jackpot meter
I am not comfortable with your terminology. I assume this means if you play $100 coin in, the meter will rise 30 cents.
how much money it actually takes to be fed into the machines to "trigger" the average jackpot?
If the jackpot is currently at 800, then expectation is: it will drop at 900, which mean 100/0.3%=$33333 more coin in.
If the jackpot is currently at 900, then expectation is: it will drop at 950, which mean 50/0.3%=$16666 more coin in.
If the house edge is 10% then does this mean in actual fact it becomes 110% of $5800?($6380?)
If I assume my original assumption that if you play $100 coin in, the meter will rise 30 cents, then 174/0.3%=$58000
The house edge makes not difference because $100 always equal 30 cents.
My understanding WAS jackpots in New Zealand slot bars are controlled by gangs. They will physically hurt you to scare you off. I heard stories of people end up in hospital for few days but not life threatening.