Rare+ SemiRare phone valuations,rising, falling or staying same over last 15yrs?

[rfkimba]

Dear Telephonists,
Are there any articles or references that address changes in rare/semirare collectable phone valuations over time?

As I am new to this hobby after collecting coins form many years I have been given a series of reasons why phone values are rising or falling. They are:
1) True rarities like the WE #10 in original condition, excellent condition potbellies hold their value or appreciate with time based on supply and demand and the fact that many people have less  disposable income won't affect their pricing unlike lesser phones;
2) The 2009 recession hurt collectable phone demand and  valuations across the board and things are improving now;
3) The popularity of EBay interchange vs traditional land based shows a few times a year has equilibrated phone values to more accurately reflect true values/scarcity;
4) People rely on EBay now more as a pricing and rarety guide rather than traditional show methods.
Any comments or opinions on where rare/semi rare phone valuations are going?
Sincerely,
Bob Farber