Discontinued boots that are available at bargain prices are less likely to be returnable or even exchangeable, and since the Konas have sizing issues, you may find you have a boot you'll have to sell in turn.
Contact lenses can be quite an investment and are often non-returnable or exchangeable, so you will want to be as sure as you can possibly be before purchasing that you can wear them.
If the camera is a pro or semi-pro camera with exchangeable lenses, reviewers must ask themselves about the lens mount.
Interestingly, this virtual currency is exchangeable for real world United States Dollars (US$).
"Labour," Smith answers, "is the real measure of the exchangeable value of all commodities."