On those matters I think the market is going the oposite direction.
For example a set made with eco-friendly materials like bamboo, on a board made of reclaim wood can actually be a bigger hit than ivory.
The problem with ivory, is that when you show it out it is more often that someone will complain about you supporting the kill of elephants, or something like that.
Alternatives like tagua that have being collected after the nut fall on the ground, so not harm is done to the tree, will be a better option, more interesting and don't have to worry about the disaproval of the pairs.
I think the restrictions on ivory and over harvested woods like ebony and red sandalwood make it harder to build a collection based on intrinsic value. If you're collecting new sets, it's hard to say which vendors'/mfg's sets will retain their value, let alone appreciate. I just started collecting recently, and I don't have the room for any 'show dogs.' So all my sets are playable. I prefer Staunton style sets, with some variations. I'm glad I got my HOS ebony Nottingham and TCP red sandalwood sets when I did, as I might not be able to afford them in a few years. I currently have about a dozen sets from 3" to 4.5", in a number of different finishes that fit on four different size boards (2", 2.125", 2.25", and 2.5"). Every time I play I try and use a different set.