Ignoring the base packages for a moment...
The other things that are currently on sale... are they often on sale? Is the 'sale' like the sorts or sales in Amazon where a book is always on sale (or very often on sale), or are the things that are on sale on sale just for December?
To take a specific example, the ESV Study Bible (Notes only) is $40 instead of $50. Is it normally $40 or $50?