I do think it’s possible to build your own house, but I don’t think you should underestimate the time, effort and costs. Most people who start down this road often do just that.
I do think that some (not all by any means) developers are over charging and if you hire an architect who then goes out and hires a builder, I doubt you will get a “deal”. But if you find a smaller contracting outfit who you trust (no simple thing to find mind you), and you want to put a good bit of your time into the project, overseeing/participating in design, permitting, construction, etc. then you could build a house at a much more reasonable cost. (Note that I didn’t say cheap, I said more reasonable cost!) If you are thinking of doing all the actual construction yourself, you could potentially save even more, but plan on working on it full time for a couple years. (Which means you won’t be making a salary)
Keep in mind hat even though many of the construction workers you see building houses are illegal and/or illiterate they do have experience and generally a supervisor who has even more experience. And without that experience, you could easily make some very costly mistakes that would take away most of those savings you were hoping to generate by doing things yourself.
Last, never forget to factor in your time as a cost! Even if you hire others to do the vast majority of the actual building, you will spend lots more time dealing with this than you might guess. And as they say… time is money.