I see this as a bad thing, and a bad thing only... no exceptions to this.
Because what it is in actuality is MICROTRANSACTIONS. In a new, stupider form. The fact that each one comes from a different source does not change this... they're still microtransactions. And ones of dubious quality, at that. I've seen mods for LOTS of games. I've used them. And, FAR moreso than official content, they can be INCREDIBLY SCREWY. Even the highest quality mods can do some really strange, damaging things when they run into issues. The chance of this happening is very dramatically higher than with official content. Even moreso with a game like Skyrim, which is already a glitchfarm to begin with.
Now, I'm fine with the idea of DONATING and such. If a mod maker has just been putting out tons of amazing stuff, people WILL donate. And there are a variety of valid ways to encourage this. Best example that comes to mind for me is Minecraft's "Feed The Beast" mod.... thing. Not just a mod, but an entire launcher of great quality that not only comes with gigantic complicated modpacks (LOTS of them), but also makes it soooooo much easier to stick more mods into any given pack if you should feel like it. Normally the process of adding a mod to the game can be... difficult. And filled with problems. Particularly if there are already mods running. I've spent hours yelling at the screen trying to stick the damn things in manually. And then this came along.... and I havent had to do that since. And what these guys have done to get money is not any of that microtransaction crap. They first built up this software, and related maps/mods/whatever of their own. They made it incredible, they got it out to people, they got it popular, and they just kept showing off just how much they could do with it. Once it hit a certain point, they simply started offering things in a completely seperate shop. Not digital content, mind you.... I'm talking actual physical things. Shirts, mugs, various things that are quite cheap to make, but that people are happy to buy because they're interesting, and they support the devs in a non-annoying fashion. You can pay for these if you want, or even just donate I think, but you DONT pay for the launcher. And of course they can do things like put up proper ads on their site to generate more money, as is normal on the Net. This, to me, is a great way of doing it. And it's working for them; the team is looking to expand even further, as it is right now.
Now obviously that exact model isnt going to work for everyone, but there's TONS of different ways that something like this could be handled in a manner that DOESNT restrict the actual in-game content. People could get creative with this. As opposed to trying to sell you new sword models, or mods that may or may not interact very badly with other mods (which can happen in any game that uses mods). Mod making is great, but I'm sorry, I'm not going to pay for something that ISNT a game as if it was a game. And really, only the biggest modders, brought to a high status by constantly making all sorts of awesome things, should be attempting ANYTHING of this nature to begin with. There's no way in hell I'm going to pay for a mod from a modder I've not heard of! Or if I research someone and see that they've made like, 3 swords and almost a castle, it's like... I'm sorry, but no. You havent proven enough to me yet, I'm not going to support you for now.
And note, this has exactly squat to do with the actual cost. I'm not in a position of having money issues. Not even close. Hell, I'll go out and purchase full-priced games at random out of simple boredom. And I dont mean the sort of boredom that occurs over the course of a couple of weeks, I mean "I've been bored for 30 minutes. I think I'll go get something new for the heck of it" sort of thing. I do this *often*. This doesnt dent my funds in the slightest; as a rule, I can do what I want, when I want. So yeah... it's not about the price. It's more about the practice.
And what I mean by that: It's just the same, again, as the microtransactions..... which means that eventually, inevitably, it *will* lead to people getting greedy, and starting to do some of the nasty things that the big publishers are doing. I dont believe for a fraction of a second that this WONT happen. And that's where the downward spiral will get going. Obviously not all modders will do this; there will be many that will rail against the very concept of this, offering tons of stuff for free simply because they have awesome ideas that they would love for others to play with, and just to support the game in question and it's community. But many will dive into that downward spiral of greed, doing whatever they can to suck up more and more cash while offering less and less, and such as that.
So, yeah... Obviously nobody has to agree with me, but I just thought I'd toss my own input in here, as someone that likes using mods in a general sense.