I've played some great mods over the years ( They Hunger and USS Darkstar, I'm looking at you ) and would happily donate to their developers. However, this doesn't sit right with me for some reason. Valve used to be very close-knit and careful about what it did, what it let people do and who it let do it when it came to Steam...
But in recent years it's opened up it's doors through things like Greenlight and the workshop which on paper seem like GOOD things to do. Yet I feel that the quality of some of the games on Steam is really poor and there is little-to-no curation/care for what it sells anymore.
While I agree that content curators should have a choice about charging for their efforts I don't know how/who is going to be able to decide if something is 'worth' the cost - it's very easy to make something look good in a review/screenshots but what recourse does someone have if a mod breaks a few days after purchase or becomes unstable? If anything I feel that it could damage the modding community on Steam because people are less likely to try things out and recommend them to friends - micro transactions may seem small individually but they soon add up - ask some of the CSGO players in that thread.
I am also surprised at Valve for ( if true ) taking a 75% cut of sales... That seems a bit Sherrif of Nottingham to me.
All in all I suppose it's another example of Valve trying to keep ahead of the curve and ride the wave of innovation - I'm no market analyst and I hope they've thought about this properly because it seems to have sparked off a lot of negativity towards the supposed saviour of PC gaming.