Argos are like this, sometimes they just have something on special at silly reductions. The other thing they've had if your kids are into them are the v2 Aquabugs (aka robot fish). They are doing a 2 pack for £9.99 or two for £15.00, so effectively 4 for £15.00 or about £3.75 each. Bearing in mind these are the new v2 models this is damn good as they are £9.99 each in Toys R Us in the UK.
As for the negative review, ignore it, we got a bunch of them and not had a single problem with them yet, I suspect the user complaining simply hasn't replaced the batteries or done it incorrectly lol!
As for the negative review, ignore it, we got a bunch of them and not had a single problem with them yet, I suspect the user complaining simply hasn't replaced the batteries or done it incorrectly lol!