Battalions have always been about giving someone who is just starting the army a kickstart with a slight saving. As such a cannon is much, much more use than a worthlessly small unit of greatswords.
10 Greatswords was a stupid thing for a new player to get hold of, to even begin to make use of them you need to triple the size of the unit, which means spending another £50 just to get the unit off the ground. Cannons on the other hand are an absolute staple of the list and are a great thing to give a new player. Add to that what vaguely competent Empire player would include a unit of greatswords below about 1500pts minimum anyway? They're generally something you add in at higher points value games, if ever.
It's a shame handgunners are in there, but I guess GW is still in denial about how badly they have nerfed an already sub-par unit, and could you really envisage an Empire batallion without any knights?
And if the price has dropped to £60 as some are suggesting that accounts for the £10 drop in total value, in fact as a percentage of the original cost of the contents, you are actually saving more.
What is indeed the pinnacle of idiocy is that they still insist on packaging the knights in sets of 8, which is either 2 too few, or 2 too many for the only viable methods of fielding them.