"But, in doing so, are they at least not violating the clubs' ethics of one member not taking advantage of another?"

How can they possibly be violating anything?
The code of ethics does not set prices on Sterling Magic or chips.
Joe sells a Sands chip for $20, Bill sells the same chip for $40. How can that be a violation of the code of ethics?
What if Bill drops his price to $15? Is Joe now violating the code of ethics??
What if Joe raises his to $40 to match Bill. Then you have no chance to shop prices. Are both of them now violating the code of ethics?
If I want to charge X for something and Sam wants to pay X, that makes it OK, IMO.