OP, I'm pretty sure you meant to ask if anybody makes enough money to "supplement" their income, not "offset" it.
What do you mean by "this hobby", specifically? I ask because I think there's quite a difference between the central theme of this site and arcade collecting proper. Different customers, different knowledge requirements, different products of interest, etc.
I'm not surprised to hear that some folks are able to make an income in the servicing/repairing of coin operated machines. Even if they're not as popular as they once were, they're still out there generating money for people, and therefore need to be kept up and running by somebody.
As for the specific hobby that is this site's raison d'etre, I think that's probably a lot more challenging to make profitable and worthwhile. In the last two years I've had at least 10 people inquire with varying levels of seriousness about hiring me to build them a cabinet after they saw mine ("DUDE, this is so awesome! What would you charge to build me one?"). But with what mine cost me to build and, most importantly of all, the time it took to do it, the price I would need to charge in order to make it worthwhile would be absurd, so I just encourage them to do it themselves or buy a kit. Part of me really wishes I could do what they're asking, because I know that they look at the project as too overwhelming and just end up forgetting about it, whereas if I accepted the job of doing the heavy lifting for them I'd be bringing more people into the hobby (and, I'd have cabinets to play on while at friends' houses--haha). If I had a big CNC rig and could mass produce the cabinets, that would probably be the only way to get something to market at a price that would be conducive to the "impulse buy".
I'm not saying I think it's not possible to make money, I'm just saying it's going to take more than a love of the hobby to monetize it.