To go over 80 does get very expensive. IT is an actual Forge Point gainer if you work a lot of 1.9 for other players.
At level 100 is 1.92 and some guilds have 1.92 threads.
As mentioned the main reason is when working 1.9 threads you gain 'free' Forge Points each time.
Plenty of players gradually work their Arc up into the 130's and more. Once there I am amazed player can amass the FPs needed to continue. but they do.
And even sniping become more lucrative, snipe to gain a few Fps at 1.9 If yo are over level 80 it becomes more worthwhile