I think the shop multiplier should scale higher, I've got x63 and I can't tell the difference between it and the 2 levels before and I'm only at guardian.
I can tell that the double or nothing is built to keep you from geting loads of money form it, gambled with 50x my TpS 15 times, lost 15 times. gambled with 2x TPS gambled 10 times, won 10 times. as the wise Legolas would say from the Startrek series... "Thats no 55%!"
 "Cosmos Quest: The Origin"){kind=icon}
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Because looks cool :)