I'll point out that some of these deals actually cost you money.
The Imperials shield Infantry company for instance, if you were to buy everything separately, using the battalion boxes, you'd save your £1, plus you'd have 3 extra sentinels into the bargain, which would cost you an extra £55 to buy.
That's because the bundles aren't priced using the Battalion Boxes, or even the multi-set bundles. The Windrider Host one is priced using the single box Vypers for example.
So yes, there are cheaper ways to get some of these kits but they are priced correctly, if a bit greedily.