It’s certainly expensive, but that’s eurorack, which despite how it can seem on forums like this is still a very boutique industry driven by very very small companies making a lot of stuff by hand. As far as affordability goes, Make Noise are one of the better manufacturers out there IMO- but the TMMM features some of their most expensive but also finest modules. There aren’t a ton of great comparisons out there for self-contained 3U packages- maybe the Endorphins system, which is 10hp fewer modules with no room to expand, and nearly 400 dollars more expensive than the TMMM (though their design intentions and use cases aren’t comparable really).
Important also to consider what you’re paying for: a stereo filter module which is built out of literally 4 analog filter cores with QPAS; an infinitely versatile and very high fidelity real-time (and/or not real-time) voltage controllable stereo sampler/looper/live effect/digital tape machine in Morphagene; Maths needs no introduction for the variety of what it can do, and it’s analog which contributes to price; Woggle which is analog based on I believe two VCO’s; Mimeophon which simultaneously does (in stereo) chorus, flange, karplus, dedicated voltage controlled doppler/psychoacoustic stereo effects, looping, echo, delay of up to I believe 40 seconds per tap?, and reverb continuously variable from mild diffusion to cavernous and shimmer, with voltage controllable filtering, and all done in very high fidelity. And of course the extra little utilities and a metal case with power.
With regards to system cohesion, I actually think they are extremely well matched together and dedicated to high fidelity stereo abstract processing in a modular environment. It’s not something that is trying to be a synthesizer, in the traditional sense of the word.
I swear I’m not a Make Noise salesperson. (yet) 
