The way I see it is this: You use what you have to start off. If you see it working out in your favor, then you buy more. At some point, depending on your risk tolerance, you may start buying drives/adding connections with the anticipation of making your investment back.
I don’t think that anyone is expecting SNOs to have an exabyte of standby capacity. That’s not happening. It is used elsewhere and moved to storj as the needs grow.
The way I started: I had some spare capacity in servers. I used that to get a feel for it. When I saw that it was getting used, then I added a 4TB drive. When that started getting filled, I could have waited for it to fill up then ROI on its own. But I didn’t, I added a 2nd 4TB drive. This way both of them started working towards ROIing the 2nd drive. At that point I scrapped the idea of ROIing the first drive and kept adding. A couple years down the line payouts made it to a point where I could add bigger drives. That’s the point I’m currently at: I add 20TB drives and scrap the idea of waiting to get my investment back. Do the payouts cover the drive+operating expenses? Add more.