There is often (not always, but often) a huge difference between self published books and those published by tech publishers such as Pragprog. The professional editing and guidance alone can make a massive difference.
That’s not to say self-publishing is a bad idea. If you are an experienced writer or a good teacher, then go for it! However you need genuine reviews from people who are willing to recommend the product at the price point you want to sell at.
I would expect self-published books to be around 9 to $15 - infact that is what I have paid for most of my Pragprog books as I wait for the sales then buy in bulk 
As @andre1sk mentioned, it’s up to content creators how they price their stuff - but - it’s up to everyone else whether they buy, or not. If you have spent a lot of time on something, surely you want to maximise sales?
If you were asking me for feedback on pricing I would say price it similar to @kujua’s book at $10 Erlang and Elixir for Imperative Programmers (book published) and also give out review copies to the first XX so that you can get some genuine reviews and feedback. $249 for just a years access to very limited content seems expensive, even $29 a month is a lot for just one course.
JMO - you are of course free to price your course as you see fit 
