pedro - as a small business owner (well, till i liquidated it to move to AC), people generally like to feel like they are getting something extra. the high end makeup counters get ya everytime with their "free gift with purchase". Its not ACTUALLY free, but i makes me buy at that time. The consumers perception that they are actually making out better, even if they are not, is often the impetous behind the buy.
think of how many times you bought 2 for 1's on some item...deodorant, chips, whatever. you didnt really need two, frankly you might not have needed one...but it still makes you want to buy cause "no one can pass up a good deal".
Having said all that, i think you need to be careful that you dont shoot yourself in the foot. i think that you are right that it needs to be a fairly onerous offer lest people just wait for the 'special' in order to buy at all. FOr example, there are certain stores in the states that ALWAYS run a sale...you NEVER pay "full price" cause you know in a week it will be on sale. The retailer has essentially trained the consumer to be a wee bit patient, and they will save (or at least have the perception of saving).
not sure if this is the opinion you were after, but its the one ya got!
