Hmm, they've been making their plans worse? Their new Magenta plans I think are a bit worse than their previous One plans. I thought the One plans included 10GB of LTE tethering per month (I might be wrong though) and then if you paid an extra $10 on that line it'd be unlimited tethering (but they might throttle you after the like 50GB). The Magenta plans only include 3GB tethering and then only 20GB if you pony up the extra $10. (Looked it up, hmm seems One plans only offered 3G tethering, and the upgraded offered 20GB LTE tethering.)
Just noticed the upgrade is $15/month/line. Lame.
I know at one point you could get like 6 lines for about $150 (because I tried to get one of my sisters to switch over from their pre-paid where they were spending like $150 for 3 lines and it was more restrictive about data than T-Mobile - and since a lot of their data used was from streaming services that they'd get unlimited on T-Mobile it was extra beneficial), but 5 would be $180 right now.
So you don't get any corporate discount any longer, or did they switch carriers or something and you want to stick with T-Mobile? They had an "offer match" thing on their website but of course it only works when switching from the other carriers so it wouldn't help you.
You might call, as I think one of them included DoD as qualifying for military discount (unless there's some specific line there, but I recall an ad from one of the carriers that specifically mentions DoD in the military discount). That'd get your 5 lines down to $110/month. You'd also get Netflix (but single display non-HD; you can pay extra per month to get the HD/UHD though). I doubt it was T-Mobile as it doesn't mention DoD anywhere on that though.