I don't know what they charge for Gluhwein at a proper German market but I bet it's less than 6 quid, which seems to be the going rate for half a paper cup round here! Food is outrageous too, and mostly not worth it.
I'm VERY humbuggy about Christmas Markets in the UK now, mostly because the ones I've been to are a bit shite. Basically what I expect is something along the continental North European model - so I want a few stalls selling German/Swiss wooden ornaments, those incense smokers and candle holders, colourful paper star lights, glass decorations, gingerbread stalls - and some decent crafts that are worthy of the term 'craft'. Proper artisanal stuff that's made by the sellers or at least in the UK, something that takes skill and years of experience - pottery, silversmithing, quilts, wood carving, mosaics, handmade candles, etc. When what you get is rows of stalls selling bought-in dross that was made in China, mass-produced tat, and 'craft' that basically entails someone going to Hobbycraft or Baker Ross and buying tacky supplies and then glueing it onto other stuff.
Yes, I'm a crafts snob!
Decoupaged wine bottles, glasses with gems and glitter stuck on, diamonte pictures, plaster cast trinket bowls - they give a really bad name to 'crafts'. I make rather nice things that I sell for probably too little, and people printing AI images onto polyester cushions and tote bags next stall to me are charging mad money for it. I should just stop, really. It's sad.