But what if the dealer says "It books for 900 but I'll let you have it for $800."? Are you going to assume that the chip must be real and peel $800 off your roll and hand it to him?
What the undetectable repaired chips do is make all the chips of a particular issue, repaired and never canceled, worth the same price. That price will be based on the number of chips of both types believed to be in circulation.
There are now 476 chips on the canceled chips page. I probably won't buy uncanceled versions of any of them. But if I do it will be for the repaired price.