Random thoughts for gem-buildings
1) Recycler.
Recycler needs 990gems, and provides a steady infinite source of coal. Nice instead of searching and building coal mines all the time.
10 licences however, worth 650gems, and are much more usefull. Pinewood chain production is also alway steady (never runs out) so with 4-5 buildings you have the same infinite, same rate, source of coal. And you still have 4-5 licences left, for other buildings.
2) Noble Residences Deed / Friary. Same goes here. Friary costs 2450 gems, Noble Residence Deed costs 95gems. 10licences can give you same benefit much cheaper and have some more licences free for other things. Maybe Noble Residence Deed, is usefull, (95 vs 65gems 1/10 of 10 licences) if you acquire gems slowly through levels, so you cant wait to get the full amount of 650gems.
Am i missing something here or what? Getting more licences is THE way to go, for most of cases.