Years ago, I remember speccing up an 8 core mac pro which was a massive number of cores in the day. I figured I would justify the £7K cost as it would last me 'forever' and I would somehow be so much more productive with it. A true pro lol.
Thankfully sense prevailed and I never clicked buy. Zero regret in hindsight.
Its so easy to talk yourself into bigger specs.
The M6 would suit me fine I expect but Im disappointed that they made TB5 a pro only feature. Anyone who has bought one of the new studio displays recently and wants 120hz might need TB5, especially if adding another screen.
As for the cost. It's one of those things where you will find a way if you want it sadly. Otherwise , older M4's (perfectly good) are probably still around at some places.