Get off it, mate. First of all, you're not entitled to free mods simply because they're mods or because you want them to be free. The modders are the ones putting in the hard work creating content for you to enjoy and for that you should be appreciative. If they suddenly decide they want to get paid for your work it's not your place to bitch and moan - you should just suck it up and accept it. Maybe you'll support the guy who gave you your enjoyment or maybe you won't, but he's not your slave to provide you free stuff out of obligation or the goodness of his heart.
A lot harder to put hard work into mods when you can't trust other modders with your own work anymore. Consider how many individual assets goes into making a mod: models, textures, sound files, and scripting; many fellows can script, some can even both model, texture, and rig a whole working object into the game, and for those who are willing to put that amount of effort the action is commendable. But, the average modder cannot do all these things at once, and requires assets other then what they can create alone in order to complete their mods.
If modding becomes polarized (perhaps the most tragic portion of this ordeal) between payed assets and free assets which are limited to be used for mods which are also released for free, these fledgling modders will either have to pay money out of their own pocket to complete their works, or disregard the system entierly, placing them in between a rock and a hard place. This also puts limits to how complex a mod can be; thousands of assets that appear to only cost a few cents start to stack up into hundreds of dollars worth of content, for a single mod that
might break even if enough people decide to buy it. And this is assuming that they don't simply pirate the content outright, undermining the supposed "point" of this venture in the first place.
Also, there's the gammut of the fact that in order for a modder to profit from this system, they have to make at least 400$ worth of revenue; until that point, Steam witholds all money earned, releasing it in increments of $100.00 USD each. If sturgeon's law has any effect on things, the average user won't see a nickel while Valve and related parties reap all the profits from their works; this means that say, some fellow decided to release an unofficial patch to fix some game mods? At best, this costs the developers of the game nothing and they in essence have someone develop their game for free, at worst they're actually
gaining revenue from putting forth a lack of effort, ultimately degrading the ethics of mainline developers, and placing content development on the burden of the modders.
Allowing modders to get paid allows these people to remain working on mods more often, plus it could get entirely new people into the modding scene. Then people will start competing to make the best mods at the lowest prices and the consumer benefits in the end. Capitalism at work, right there.
The sort of people you seem to be refering to, those who would attempt to join in order to make a profit, are unlikey to make the jump for a multitude of reasons. First of all, joining in late to the party gives them the above complications of having to pay other people for assets in order for a mod in the first place if they want to sell their mods at all: rather then by their imaginations, modders will be hampered by their budgets, without the knowledge benefits of an actual game developing studio. If anything, the only people who would turn any sort of a profit would be the elite who managed to scrape a high ranking during the early period of this movement and perhaps model makers if they're lucky and not instead have their models taken for no compensation.
As a modder myself, I do concur we should be allowed to ask for money for our work (remember to donate, lads), but certainly not with this poor excuse of a system. In fact, there wasn't any quarrel over the donation system when it was first instated, so why change it? Furthermore, the state of the community would indicate that any modder that actually attempted to seriously pursue this route would also be ostracized from a significant part of not only the userbase, but also the modder-base as well. Regardless of how you feel over this,
is money really something worth sundering the community apart for?