The value is determined by the chip and the location
and whether the chips were made for that game at that location.
The value varies on chips whether they are hot-stamped with
just a monogram or address number (known or unknown), a name
of person or club, city, inlay, Crest & Seal, paper, plastic,
etc.

The value will be anywhere from worthless for plain, unmarked
chips to several hundred dollars for a nice Crest & Seal.
The average illegal monogram chip is worth $5-10 IMHO.