Last year it was 20% off across the board, 30% off orders over $100, 40% off over $200, and 50% off over $300.
I loaded up to around $170 or so...then added a 1/32 Tamiya Mustang that took me just over $300 - for a total of $150.
If their sale this year is anything like as awesome, wow. Also keep an eye on Sprue Brothers...they tend to do less structured, but with really deep discounts on a few items.