The 4 disk version (Magic Makers) is poor in comparrison to the 5 disk version and maybe this is why it's being given away? After all, it hasn't been around for long in comparrison to other disks.
The best shipping that I've had from the States is when buying from Hank Lee's Magic Factory. Took about 4 days from memory and this in itself seemed to be a piece of misdirection as I wasn't expecting the parcel so soon and was actually wondering what could be inside as I didn't remember ordering anything else
Personally, I think that Penguin has gone down hill a lot in recent times and again, their 'in stock' status mentionned by Shaneking is perhaps an indication of this.
Although worth a mention, I don't think that this deal is particularly a bargin as I'd struggle to buy $100 of Penguin material that I'd get good use and value for money from.
Perhaps it's a classic case of CUPS

Member of the Magic Circle & The 2009 British Isles Close-Up Magician of the Year
It's not really an optical illusion - it just looks like one!