I'm thinking the Workshop is tempting:

Current L21 Workshop: 1132 Pop, 589 Culture, produces

**3360 in 3 hours**
Magic Age 8 Workshop: 1330 Pop, 693 Culture, produces

**6042 in 3 hours**
It's the same size, costs 900 Diamonds. And - if this is possible - says "RESALEABLE".

If this is accurate...well, I'm interested.

The Residence numbers seem low for the cost:

Age VIII 4x3 size +pop 1710 , 455 culture required 1400 diamonds!

85500 in 18h 51m

For 2800 diamonds you get 3420 pop on 24 grids (2 magic residences)

For 3000 diamonds you get 2900 pop on 24 grids (Snails) PLUS 3200 culture

Basically Snails give all the culture for free...plus they're so easy for NH that the users find it easy to maintain a culture bonus.