Hi Chan -
Price and value are two different things. There were a small number of these exact chips recently discovered and sold on the board (http://www.thechipboard.com/index.cgi/md/read/id/1134340/sbj/la-rue-casino-50-s-vintage-poker-chips/). So while they are still valued at a high figure in the guides (and I emphasize the word guide) the cost of the chip, and ultimately the price you could sell if for would be far less.

Like all things its supply/demand/condition. Your chips have a little bit of wear on the hotstamp that will take away from the price, but given they are old Nevada house chips that are highly collectible they are still in demand. Unfortunately the supply is a little bigger than it was a year ago.

Maybe its a good start for a collection of your own?