According to Art Anderson's Casinos and their Ashtrays:

Caesars 2-6 dollars
Castaways, depending on style, 8-12 dollars (3 snifters) or 5-7 dollars, looks like a gogged gear.
Tropicana-need more info
Pricing is 8-years old, and very, very subjective!

What are the other ashtrays? Any scans?
I may be interested in the Castaways.