As for the training manuals, they might be useful in the hero academy (as well as other Mats of which we currently have way to many)
Concerning the high gem cost. Yes, if you want one specific ascension mat and have to pay 300 gems, then it’s quite a lot. However, if you have a huge surplus of one of the mats but several others would help you, you don’t need 7 rolls on average (and thus 2100 gems) but maybe two to three rolls in order to get something much better. Then 300 gems per roll isn’t that bad anymore (still a bit too much)
Like almost everybody, I definitely do hope that the gem cost will be somewhat lowered (brew time and food cost might be increased for that). But like @BarryWuzHere I agree that we had to expect that SGG won’t give us tons of great Mats for free.
I think a modest amount of gems + high amount of food for getting a chance to convert 3* farmable stuff to 3* non farmable and maybe even 4* non farmable is absolutely fair. Same with converting 4* into other 4* Mats.