The fall in flash memory pricing is continuing with basic 64GB USB 2.0 flash drives now costing around £17, while 32GB microSD cards can be had for as little as £8.75. That's not far from 4GB per £1.
In comparison, an external 320GB hard disk drive - like the Buffalo Ministation 320GB - costs around £50 or 6.4GB per £1, which means that flash and magnetic storage are close to parity.
Interestingly, we have yet to see higher capacity flash drives or microSD cards swamp the market. 128GB drives are still quite rare and carry a significant premium despite the first unit being released nearly three years ago. Ditto for 64GB microSD cards that carry a "per GB" price thrice that of a 32GB model.
USB 3.0 drives are still carrying a small premium compared to USB 2.0 ones, and for very large capacity drives, is the preferred option, especially if you plan to transter large chunks of data regularly.
Similarly, the price of SSD storage devices has fallen significantly over the last few months with some models flirting with 50p per GB.
Bear in mind that you should be able to combine 10 USB drives using a USB hub to form a massive 640GB virtual hard drive for as little as £170 (or 384GB for just over £100).