Recent Tire Ashtray Prices from eBay:

Rare Vintage Tire Ashtray, Overman - April 4, 2004 - Bids: 13 - Final Price: $338.00
Early 60s Fisk Tire Ashtray - Never Used - April 11, 2004 - Bids: 16 - Final Price: $189.05
1934 Chicago Century of Progress Tire Ashtray with box - March 28, 2004 - Bids: 21 - Final Price: $152.50
First Choice of Farmers, Tire Ashtray - April 11, 2004 - Bids: 22 - Final Price: $129.49