Well I just got the final boss in RFJ, besides killing darn near everything and not dying, you also need to get into x-medal mode (where the little badges turn into the gold bars). I was in practice mode as well, so it's possible. I managed to get 10 mil, however I was WAY off 50 mil and nowhere near 100 mil (checking the boards makes me think I'm never going to get it as I can't seem to pickup the medals without dying). The x-medals increase by 10000 for each one you pick up, but only if it dropes AFTER the last x-medal you pick up. In other words, if you have 1 x-medal on the screen and you pick it up (worth 10000) the next one that drops will be worth 20000. If there are multiple medals on screen at once they will all be worth whatever the value was when they dropped. If you miss picking one up (it falls off the bottom of the screen) they reduce in value back down to 10000. Hope this helps.