Can’t say I agree 100% here. Xhaka is a much better passer of the ball than Kramer, and has created more in terms of playmaking from that position last year, than Kramer does this year. Other than that, you’re probably correct.
As for the transfer fees, there are a few factors worth considering. Leverkusen, as I recall, were pretty sympathetic with Kramer leaving, as they had alternatives in Bender and Aranguiz (haha), got Baumgartlinger cheap and probably thought they could replace him quite easily. Not particularly clever planing, but whatever.
Xhaka, on the other hand, was quite central to Gladbachs season, being by far the player with most touches and passes. Leverkusen bought Kampl, who I think is a better player than Kramer, and who had even one year more left on his contract, for €11 million from Dortmund. BVB wanted to get rid of him, and did not demand a lot.
You also have to consider how the windfall from the new tv contract made PL clubs splash significantly more cash, simply because they could afford it. Transfers within Germany are still a lot lower in price. So I don’t think you can really compare the volume of these two deals.