That's not true... otherwise people would just go 100 mph all the time.
If you speed at that level constantly, you will almost certainly be caught at some point, unlike marijuana usage where the odds of being caught are quite slim, and thus a slim penalty results in next to no deterrent. Also speeding tickets increase your insurance and can eventually lead to license suspension. Here you pay a $100 fine and forget about it. Not much of a deterrent unless you're a poor, to me a $100 fine means I have to cancel a strip club visit or record store shopping spree, it'll piss me off, but it won't stop me from doing anything I like.
Do you really want to open this debate?