We may have been talking at cross-purposes. Yes you can get the trip a lot cheaper but not for the day. The best you can do independently to get back quickly is fly back the morning after.
With TC/Spike you're paying for a night flight, Manchester direct to Cologne and no hassle transfers to Gelsenkirchen or the stadium. That's attractive to older people who don't want to be messing about or even younger ones who like the convenience, people on their own who can't share costs and people who need to be back at work the following day.
Comparing like-for-like (TC v Spike's trip) showed similar pricing. I've just checked Skyscanner and the best you can get otherwise (to get back early the following morning) is flying Manchester to Dusseldorf, arriving 09:30 local time, then flying back from Cologne at 06:55 local time the following morning arriving back at 07:30. That's £252 but there's no transfers.