That's for two reasons. Firstly, a lot of the sale items are 'special buy' and to be honest, we're not sure if these are good deals or not. To be fair, they probably are cheaper, so worth a look. But there are also good sale markdowns too.
Anyway, we have examples of both. Above is the midcentury-style House by John Lewis Tina Floor Lamp. That was fairly modestly priced originally at £25, but is now a steal at £12.50. Alternatively, check out this amazing retro KitSound Jive DAB/FM Portable Radio. This seems to have passed us buy in the past, but it's available in this lovely shade of blue as a 'special buy' at just £59.95.
Plenty more where that came from. See the John Lewis Clearance for all the deals.