Here in the UK the genuine Rubik's Cube is massively available for £10 from mainstream stores (e.g. Argos). Anywhere that stocks 4x4x4 and above is somewhat more rare. Internet shopping seems to be the key for the harder to obtain cubes.
Ethical shopping?
I live in the UK and anyone who knows me will tell you I'm not made of cash but moreover I tend to think long and hard before purchasing something as it's not just money that is the cost of consumer purchases but natural resources come into play: manufacture, transport, packaging, warehousing -- all energy consuming activities!
If something has to come half way round the world in order for me to enjoy it, then I may forgo that enjoyment -- after all there's a lot to enjoy out there that doesn't cost the earth!
All that said, I'm still a sucker for cool things!
Cool things...
Whilst searching for cubes I happened to pop into a Jugglers in Nottingham. They stock mostly juggling equipment (no surprise there then!) but also lots of puzzles and novelty items. I asked them if they planned to stock cube puzzles and the guy said "I'll have some in by next week"! Whether he was already planning to stock cubes or not I don't know but sure enough, the next time I popped in they had 2x2x2 and 4x4x4 cubes in stock. They turned out to be EastSheen cubes which are regarded as good quality among speedcubers.
"Get a DIY Type-D with a Type-C core or the old Type-A; not the new Type-A: they suck!"...???
I planned to try out Cube4You (aka "C4U" - http://www.cube4you.com/ or http://cubefans.com/ - same shop with a more compliant website!) as it is well respected in the speed-cubing community forums at http://www.speedsolving.com/ . A few things put me off buying from C4U: postage to the UK is pretty steep and there's quite a long delivery time. Also there are a gajillion different types of speedcube and whilst there is some concensus about which types are good and which are poor it seems hard to properly identify which types are which when it comes to ordering and for someone new to this world I'd rather not have such an open choice!
Eventually I came across a UK-based online store: Puzl -- http://www.puzl.co.uk/ and after searching the speedsolving sites for reports (positive or negative) I decided they were certainly work the risk!
Early October 08 I got a speedcube and megaminx combo offer for £24 inc VAT & postage and they're fantastic!
29th Dec '08 -- I've now had a couple of excellent cubes from DealExtreme in Hong Kong: they ship worldwide for free and so this Type-C DIY cube: http://www.dealextreme.com/details.dx/sku.16433 costs only £4.46
These are all decent DIY cubes...
* http://www.dealextreme.com/details.dx/sku.16432
* http://www.dealextreme.com/details.dx/sku.16433
* http://www.dealextreme.com/details.dx/sku.16434
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Other online stores (not yet fully checked out)...
http://mefferts.com/ - a highly respected puzzle manufacturer and the only place to obtain a perfect Megaminx. The site claims that 6x6x6 and beyond is impossible! (checked 18/08/2008 - are they out of date or just misleading?!!!)
http://www.thesharperedge.co.uk/Rubiks-Cube-4x4-p-16223.html
http://www.9spuzzles.com/