Many publishers offer book packages to facilitate ease of purchasing. They usually consist of a teacher guide and assorted student books, and are grade and subject specific. If we have enough demand for a particular package or curriculum, we do our best to re-create it and match or beat publisher prices....or at least offer something competitive!
Be aware: there's a good chance you don't need everything in the bundle. Sure, there's a discount for buying the whole shebang, but because you'd be buying everything it'd still cost more than just purchasing one or two books. Spending more to "save" money is almost never a good policy. You'll have to use your own judgment, but take into account whether you really need all those lab manuals, activity books, and whatnot.
Please note—these prices are only guaranteed for books that are in stock (prices do change on us sometimes) and these discounted prices cannot be combined with other sales, discounts, or specials.