I work on 3D models quite often, as well as with those who also make 3D models. I did make the mistake of not being specific about what aspect of 3D modelling I was addressing, so I will correct that.
Making a 3D model from scratch can be down within a mere hour, plus 1 more hour to carve carve the basic shape, plus 2 more hours to map our and properly texture. Actually, texture is perhaps the easiest part if you know what you are doing. Of course, if you're not too familiar with all the tricks of the programs you use, this could end up taking up to 6 hours total or more.
On average, a basic model can be made within 3-4hours - Meaning the 100USD pays for what would be between 25USD-33USD hour of work, which is fucking stupid but I'll dig into that later. This is just the minimum price, I've seen worse models sell for over 300USD a pop.
Yes, equipment costs money. A decent PC capable of rendering these models would run about 600USD(or 1000USD if you want a kick ass GPU), because you'd be out of your mind not to build one yourself(But if you work in a studio, this also shouldn't be a problem). To note, you already paid for this so it has no effect on what the price of products produced by it should be. Moving on...
Animation is a nightmare. These will easily run up and over 100USD. Whole teams are formed just to do this one task, so needless to say any sort of animated 3D work comes with a hefty pricetag. This is also why models, skeletons, props, and their relevant animations also get reused, reskinned, etc quite a bit.
So otherwise, the pricetag on just the model alone(even built from scratch) is fucking stupid for one justifiable reason and just one only: You're trying to pay your bills with it.
Which means that you have no sort of fixed income and you have terrible priorities because you allowed yourself to enter that kind of lifestyle. The standard price on a basic model shouldn't extent 40USD, detailed ones shouldn't extend 80USD.
In Garyu's case on the 2D perspective, what he has done is actually the exact opposite. 5USD for what you're getting, despite how disappointing it may end up being, is certainly an acceptable deal when you have to factor in things like time, resources, etc. Little effort, little cost, little price. Standard drawing idle around a fair 10 USD, animations which are drawn frame-by-frame vary depending on frame-rate and duration of unique content(not to be confused with loops). However, like with 3D works, animations end up getting reskinned or reused so their face value depletes to say... The 5 USD Garyu is asking for.
But why is this still a poor value? Because the animation that is being reskinned can be located at no cost, aside from your own time and effort trying to find it buried in the internet.
In Garyu's defense, he's offering a decent deal and I myself was considering perhaps tossing a meaningless 5USD for something that rarely shows up in flash format anymore - That being an Anubis-based character. However, his actions here have been far more entertaining and he's been willing to offer us more with no additional cost so I think I'll just hold on to that 5 USD, at least until this train has run out of track.