but, and no offence meant Keith, not quite as described is it - you're saying that someone has to buy 400 quids worth at full price, then they can get up to 600 quids worth at half price. So they get 1000 quids worth of records for 700 quid. With my rusty maths, I make that a 30% off sale, and that's 30% conditional on a minimum £1000 spend
If I have misunderstood it, please clarify (as this might be what is putting some buyers off!)