We've been confused by cards like Blindfold, Bold Haggler and all the Chameleon cards.
The rules say that a cards printed value always is the one counted when buying cards. This would imply that Bold Haggler and Blindfold do not modify the buying "power" of a card, but instead the stack building value.
For clarification: is a cards buying power always it's own printed value or whatever value after modifications through dice or copies etc.?
I don't know where you get the word "always" from? My rulebook says the following: "Your cards are worth their printed value when used to purchase new ones" (page 6). The word "printed" is another reason for this confusion. My wild guess is that the word was added because of the chameleons. Anyway, like Mikko said, the card rules overrule the normal rules.
Here are some clarifications. The number on the card is just "a value". There are no such things like "a buying power" or "a stack building value". The card effects which modify the value tell when and how that can happen. I see that some effects may give an impression about different kind of values. For example, the squirrel card Accordion says "When you build a stack with this card, you may add or subtract 1 from this card's value". I think this card text is fine.