I don't know about you, but IMHO these 'illusory' offers damage the company's reputation. For a company with integrity, I feel that a sale, should always be genuine, and each 'sale' should be better than any previous.
Of course, it can be very difficult to distinguish whether a 'sale' will result in a lower overall expenditure for the purchaser because the packaging* varies.
* by packaging, I mean (for example):
xx% off what? (Read the fine print).
Is xx% off better than (xx/2)%, plus 5 times as much OBC? (You do the calculation)
And so on...