Same thing happened last year - Argos have just reduced a selection of games across all formats, but it seems that they're not only reduced, but you can buy 2 of the reduced selection at an even cheaper price. Also, the more you have in your basket, the cheaper some then appear to become! eg
PSP: Pro Evolution Soccer 2008, Simpsons & Fifa 08 are all now reduced to £14.99 - but add any 2 for £20 - making just £10 each!
Fifa 08 is reduced to £14.99 but buy 2 copies and they're just £12.50 each - handy for a mate!
Likewise, Fifa 08 is reduced to £12.99 but put 2 in your basket and it comes to only £9.00 each.
There are quite a few others too but am still 'experimenting' which ones and which combinations reduce further once in your basket.