Alright then!  Will answer you on topics, numbered. 

But before that, since English is not my primary language, I want to let you know that I believe you have the right to ask this question because you are a consumer. So I'm not answering you in a defensive way, I'm really trying to do my best to give you a proper answer ^^

I think that is some positive point of an indie developer/salesman (don't know what I can call here xD). I can answer you that. It's like when RMMZ was released, the consumers complained about the price(me included), but I don't remember seeing any open/public answers from the developers justifying the price. I guess that is normal behavior of a "big company", which I'm not. Now let's go to the answers! ^^

1 - I came to the conclusion that $3 dollars was the wrong price. It was too cheap.  I realize that my time, my knowledge, and my work are worth more. The minimum price that I will sell my plugins now will be $8.

2 - Itch io together with taxes from my country, and currency conversion,  takes around 35% of anything that I sell. 35% of $8 is $2,80. So selling a $8 product I get $5,20. 

3 - I can see that $5,20 is the right value I should receive for my work: Coding(Learning how to code, learning the RPG Maker code), publishing(Creating and customizing the Itch io page, the image covers, etc.), client support(bug fix, answers like this one, help file, sample project, and etc)

4 - I'm an indie. I do not have anyone to write a help file for me, manage all the publishing of my plugins, etc. What I'm trying to say is, I'm not a professional "salesman". I know how to code, that is for sure. But everything else I make on my own. I don't have anyone to help me. So I guess $5,20 for all that I do that involves the plugin maker work, is a price that I can be a minimum satisfied.

I guess that is it ^^