Costco does have a website but it doesn't tell you anything. I have been to Costco, and on the whole it is no cheaper for most things than anywhere else, with the exceptrion of tyres, which you will not find very useful on your PC. You also have to pay approx £30 'membership', Do visit your local store though, if only for the experience.
There are no problems with the "Insite" offer. If you qualify then you are entitled to buy under the, Teacher/Student licence terms.
Insight ask no questions whatsoever, you pay your money and receive your product. It will activate without any questions being asked of you from Microsoft. This is Microsofts way of allowing as many people as possible to use it's products. There are very few people who do not qualify, as most are, or have someone in their family giving/receiving education. j.