For individual Preptests.
I'd purchase them off of Amazon. You can get them new from the same source for the same price. If you sign up for the Amazon Prime trial (free for three months) you can get free two day shipping and 1 day shipping for just 3.99/item.
Works great for the LSAC prep tests. I decided on Sunday to get two more Prep Tests (#55 and 56) and had them arrive today. All I paid was the $8.00 for each. No charge for shipping.
I'd sign up for the trial about 2 months before your test date so any last minute prep materials you might want can be at your door in no time, at no additional charge.
I also got my wristwatch this same way. Ordered it on Thursday, had it arrive on Monday (no shipping Sat/Sun).