I used to make these same suits using the kit that Schuurkes provided, and did a few modifications of my own.
These sell for big dollars because the people who buy them know what they are looking for. It also probably counted for something that Schuurkes was one of the 3 (now 2) major Spidey suit makers, and his video on youtube has 2 million views. To your eyes it might be "same quality for $X" but I can garauntee you that it was not. There are so many different variations to the quality of these suits you wouldn't beleive it.
When I made them, the kit of pieces was $1000. Mine sold for $4000 completed. It almost wasn't worth it to be honest; given the amount of time and effort it took to complete a suit.
It took atleast a couple hundred hours of sewing on a surger, painting the tops of the webs silver, and gluing the webs onto place. Even after all that time, most people who made these suits came out with a dozen or so major flaws.
These costumes are not nearly as easy as you think.. it's simple concept which makes it extremly complicated to do right.
I do not miss the hundreds of tedious hours it took to put one of these together.
Jedifyfe- Schuurkes more than likely posted that photo to show how the suit is put on and taken off. The suits have a "blind zipper" so it looks like a normal seem not a zipper. One of the biggest questions I got when selling a suit was "How do I put it on????"