First helmet build ever.

As the title reveals, I'm going to attempt at my first helmet build ever and had some questions. What I am looking for is tips and guides.

A little backstory, my goal is to do a ROTJ costume and have set myself a project time for 11 months.
The reason why i chose to start with the helmet is because it''s the one area I don't really have much exp. and honestly the helmet looks to be like a challenge.

So I done some research and got a tip to this site which now everything got way more easier (thank god for ya'll)
After reading some posts on the helmet it's seems to be be diffucult to build one, my goal is to have one in platsic.

From what I understand I need to build a cardboard model and create a mold out of it so that I can create a plastic model from it, which to me also seems to cost a bit.

My question is what does it cost to build your own helmet vs. buying a helmet that I can paint myself ?

That is the only part i could consider buying since i lack the "expertise"

I am still building a helmet, so far in bondo, resin fiberglass, primer and sandpaper/ blades ect. - about $75.00
Hours spent - about 40 hours
Beer - about $100.00
And I still haven't bought the material to mold and cast.

But, I enjoy making things so for me scratch building is worth it.

If you enjoy making things and don't mind spending enormous amounts of time cutting, gluing & sanding then I say go for it.

On the other hand, by the time you add up what your time is worth, you could probably buy a nice helmet from Animefan or one of the others who make high quality replica castings of the original helmets. As for me, I just like the thrill of seeing something come together...it's like Ive unlocked some kind of secret or something...plus if it turns out nice enough you could sell some to friends and support your hobby!

Haha seems to be a great build at least.