Sounds like a good service, but it's a bit over priced. The same style proxies are available for a fraction of the price. But I can say, mobile proxies are the gold standard if you're using them for automation on pretty much every social platform.
If one is doing client management, then this would probably be good buy. As far as running hundreds, or thousands of accounts.. it's just not practical at that rate. I would recommend using between 10-15 accounts on one IP... using 20 would be pushing it