Hello! I'm also a gamedev that also lives in South America just like you, and truly $3000 for a year lets me live comfortably. 
I'm kinda confused about your pricing model because it's very different from your portfolio work at DeviantArt, as others said before, try showing samples and examples of what you said on your price model. If you know how to model an asset from the start, rig it, apply textures and etc etc etc and later insert that onto the game engine, make it functional, so show exactly that! Like I'm a pixel artist, so you will find samples of spritesheets and tilesets on my portfolio.
But, I sightly disagree on your prices. I don't think they are high, they are somewhat, low.
Some pointers:
1- Usually a good way to see if your price is to steep is to look onto the price models of others and compare the complexities of the work made. So, If I see that the average indie pixel artist charges 30$ for a single 90x90 sprite, and maybe I'm more of a begginer, then I will charge a bit less, like, 15$~20$. 

2- Unfortunately Itch.io tends to not be a fair way to measure the price of your work because as Evolutionary Games pointed it out, most of work offers here are for free. Search for job posts and offers in others places also directioned to the indie developer. Like, if you hoped onto GameDevLeague discord a few hours ago, you would see a job post where a Dev was paying 200$ for 3d lowpoly models (which seems to be your area). Each.

3 - Another way to measure the price of your work is to also search for what's the average salary in the area that you want to work on, on the country that most of your clients are from. Because it tends to happen that 3rd world countries have their own currency pretty low compared to those of the 1rd world, and if a client would have to pay for a certain price in their own country because that's what's worth there, why they should pay less when hiring people from other countries? Not only this promotes the lowering of the basic wage for that service on the country that hires you (if the average american pays 20$/h for a begginer 3D modeler (3d modeler salary in United States) and can pay 5$/h for a brazilian, which is pretty close to four times the value of the minimum wage, and of course we are talking abouth a hypothetical client that has the necessary budget for them, they will keep hiring brazilians while still trying to lower that wage (Some outsourced studios that work for Riot Games has their employees receiving the minimum wage, which is around 1,45$/h) but also has you receiving less than you possibly could.

4 - But again, Evolutionary Games has a point. Most of the clients that I deal with, doesn't really have the budget for the average gamedev, so it's okay to charge less. I usually charge around 10$~15$/h and measure up how many hours it would take to do each stuff. A simple 32x32 spritesheet, with 4 frame for each direction (16) frames, then. It would take me around 4~5h hours, so 50$ sounds okay. But when a client budget is tight, I lower a bit that price, sometimes even in half, but no more than that. So, it's usually a good guess to charge around for how many hours you took to do that asset,  and multiply it by a little less than the average price of your $ per hour.

5 - While it's true you get cheaper prices at stores, remember this. You are doing original artwork for the client based around the details they want. It's an asset that you thinker to their preferences, at that's is more pricey than something that's already made and made to see in bulks. That's how people that sell their assets in store gains money as well, they expect to sell a lot more than a single unit.

EDIT:
6 - Found out that you are a programmer.  How much is my code worth? : r/gamedev Here's a programmer discussing what price to charge for what it seems an entire game. You can see beginner programmers, intermediates and experients ones teling how much they would charge.

So that's all I have to say. Be more clearly on what you create with what has on your price model. Search for the right clients that has the budget that's fair to the client but also doesn't give that bitter sensation that you are being underpayed.