NOT every one knows as i didnt when you buy a psp you need a memory stick to save the games my kids were disapointed when they got theres at xmas and couldn't save a single game ,
i found the cheapest place to buy them was ebay i got a 4MB for around £20 inc postage i looked in argos and they was £65 for the same one
just dont jump in and buy the 1st one you see take your time looking at them or you wont get the bargain you should be getting
avoid jumping in to buy the one ending soonest i almost spent £15 more but decided to look further in and spent just under £45 for two
IT TAKES TIME BUT WORTH IT IN THE END...