To me, chips are like buying baseball cards and other collectibles, while you hope they increase in value, you buy them because you enjoy collecting them.

Related to your second question, chips that are a R5 ratings per Camp & Wells book is only an estimate of what the authors beleive that the "known" number of those chips that are in exsitence. In my opinion, if there are 100 of chip "x", it will probably never become super rare (like a R8) only because there are so many chips in the collectors hands or market and these will never go away. Usually it is the reverse. A chip that was thought of as very rare, is suddenly not so rare. An example of this is the Tropicana 2nd issue chips and many of the old Horseshoe chips.

That doesn't mean the chip "x" will not go up in value, though. If 300 people want chip "x" and only 100 exist, then the price of chip "x" should go up. On the flip side if only 10 people want chip "y" and only 30 exist, well in theory the price of chip "y" would go down.

Hope this helps.