Everything in Eurorack costs a lot, but for mixers it's ridiculous. Just to pick two things in stock at Thomann today :
* Befaco Hexmix + Hexpander = £730
* Soundcraft Signature 22MTK = £700
The difference in capability between the two is huge. By all accounts Hexmix is a good mixer, but you pay a gigantic premium to have it your rack. If you really need that for your live show or whatever I guess you just have to pay it, although there are lots of mixers in 19" format. In the studio it's nuts.
People often say modular is a bad choice for drums, but at least there are lots of interesting options (like BIA, the WMD modules, the SSF Entities... drool) that don't have obvious equivalents in other formats. Big multi-channel mixers -- nah.
Obvious this does not apply to small inline mixers that can do CV as well as audio. Those are essential.
Latest stuff : https://soundcloud.com/user-352590333