I feel the same way and think that xx% off should just be xx% off and so forth. That being said Rockler's advertisements for such things clearly state "cannot be combined with other offers". The bench cookies being on sale is a special offer, not a regular everyday price. Again, I hear you and like the Harbor Freight method where the 20% off coupon has virtually no limitations. Amazon's free shipping with a certain purchase price can also trip you up; some items qualify toward the free shipping amount required and some don't. Neither Rockler or Amazon try to hide this, the info is usually right on the front page of the mailer or the web page showing the offer ;-(
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke