$600 is only for the N810. The N800 goes for around £130-150 in the UK. Play.com has it for £149.99 with free shipping. The Chumby will probably have the usual $1 = £1 thing going as well. Assuming it doesn't have that then a straight conversion to £ and then adding on VAT gives £108 which isn't that far off...

The Nokia runs Linux as well so you can do whatever you want to the software.