I would argue that the value attached to Limiter and Adept is related to the number of units available on the server combined with the number of interested individuals. Demand is high. If we had an influx of more players this value would likely increase.
Unsealing a 20k unit take about 7~8 hours in Normal if you do it full speed (too tiring in my opinion)
Say you earn 1 or 2 pd worth every hour (ma3 or something) ... theoretically 7~8 pd or 14~16 pds.
Though of course you can unseal multiple items at once. But it's also quite difficult to get that many units to unseal at once.
As for Ultimate, using a useless unit (Lore) or a penalizing unit (Limiter) in a party is pretty bad, especially at lower levels... it's kind of meh, but in some class-setup it might work.
Edit: was this before or after removal of frame kills I forgot.