Whatever the JP, put a '0' on the end and that's what you could put in to get the massive streak payoff.
Therefore - 25 JP = 250 outlay, 35 JP = 350 outlay and yes, you've guessed it, 70JP = 700 smackeroonies to get it.

I play machines primarily for fun - the financial outcome is always a massive bonus if I win big. I used to chase and get stung 6 times out of ten but now, I do not think that whacking in 50 quid without even getting a go on the board (I have put in 30 without a board on a 35JP so logically speaking, this must be possible), is totally insane. I feel that people, especially young people with large student loans or what people think is 'disposable income', will get totally addicted even more so now. They will chase and chase and chase for IM mode, Mega Ridiculous Streak and win say 200 off it This may come in a second time winning say another 100 so 300 in total. They are then very very happy - until next time when they lose 700 chasing the same streak - especially when the machines have been out for a bit and they all get chipped to play so bad that a JP comes in as likely as the Euromillions Jackpot.
All in all I think they're only worth putting in your lucky tenner and taking what you can get. Or you can get a mortgage to fund your 'habit' cos that's what we need nowadays to play them
A sad, sad day for all.......