Despite the bravado and claims, I am sure guys that scalp make more than gamblers in the long haul. Basically because scalpers never lose. Gamblers may get the big hit now and then, but they don't win money every bet they make.
Basically guys kid themselves and others when they claim to be getting rich. Either that or they don't look at their records enough.
As for middling, not enough numbers to make money at it over the long haul. To be very good at it you basically have to hit the right numbers and by-pass all the bad numbers. Meaning that if you bet evry game that the had an available middle you would die a slow death. And quite frankly if anyone were good enough to know which game to bet, and which games to skip, wouldn't need to middle in the first place. Scalping has almost come to a middling state of mind these days. Basically you have to bet numbers that you hope move your way, then find the best buy back when possible. Strictly betting scalps is almost impossible, because at most you might find a nickle simultaneously, which, while free money, isn't as lucrative as taking a lead and look to get a dime or more. This does entail gambling as you have to rely on instincts, public perception, and some handicapping skills to bet the "right" side consistantly enough to not eat up profits with all the "wrong" sides you are bound to get.
It all comes down to the same thing. Trying to maximize your returns with as little risk as possible.
Scalping also only really works in bases. Might work in hockey, but I don't bet hockey so I don't really know.
I have been doing this a long time. I have tried every off the wall tecnique imagineable. Bottomline scalping bases is the only sure thing there is. Basically because you aren't relying on anything but yourself to make money. Not a missed free thorw, or a missed PAT, or a fumble, or a clock run out situation. You simply rely on your ability to find the best number, then find the best buy back number. In its purest form you are basically bookie your self. Balancing your action to show a profit no matter who wins.
But for most guys gambling is a past time, they expect to lose. So losing doesn't bother them. If it did, they would quit. But that is the power of the human mind. A guy could be down 10 grand, hit a 50 dollar parlay and he is a "winner".