yes, they 100% do......as this is what I did! Got the 11" i7 128gb model, bought the 2010 13" ultimate off ebay for a good price, switched the ssd's and then sold the 13" on again. I've done it 3 times (twice with my airs and once with my brothers). Made a profit of £30 the first time (!!), then the 2nd and 3rd time made about £50 and £65 loss, but that's still loads cheaper than paying apple for the 256GB