Legal To Sell or Not?
Okay, I admit it. I'm confused about this. As I understand the law, it is illegal to sell products based on existing properties. For example, if I were to make dolls of a licensed character such as Wonder Woman or whatever, I would be in big trouble with Time/Warner. I get that. But at the same time, I'm seeing various websites that engage in the sales of cosplay costumes based on comic book and movie properties.
The reason I ask is that I do make cosplay costumes, but have been limiting myself to mostly making them premium content over at DeviantArt because I've seen other artists there doing the same. But I've also seen other artists expanding upon this, even setting up their own websites to sell through. For example, guhzcoituz over at DeviantArt has his own website for the sale of such costumes. So what is the legality of this?

Comments
Legally, it's profiting off other people's intellectual property and therefore a breach of copyright.
Generally, people get away with it by simply not being high profile enough to be either noticed and/or worth the cost/potential bad press of taking them to court... and the fact that you often simply don't hear about the people who didn't get away with it and quietly folded when they got a cease and desist letter they couldn't afford to contest.
It might help to live in certain countries when you are doing copyright "sensible" stuff...
Often companies/ right holders tolerate non commercial "fan art", but at least you are responsible for your creations.
Platforms have their "Tous" and are mostly not responsible for their users, they just have to take things down by request.
(if you are living in the European Union, Art. 13 DSGVO might become a game changer for platforms/ forums)
Personally I wouldn't do it, living in a country where they can sue you for copyright infringement.
A forum is not the wisest place to seek legal advice. We would suggest that you speak with a lawyer as most here can only give you anecdotal information which may or may not be correct for your situation or locale.
It's not legal. If you understand that you would get in trouble with Time/Warner for doing WW, it's not that big of a leap to understand that you would get into trouble with any copyright or liscense holder for any 'cosplay' outfits if you are selling them. That includes cash up front, 'donations' or other forms of point trading. It's pretty unethical to make $$ off of another person/companies characters as well. I mean I get it, some of the cosplay artists put a lot of time, skill and effort into making the outfits (assuming they aren't just ripping them out of a game) and would like compensation but it still isn't legally allowed.
Same goes with the art created using 'cosplay' items. Most companies ignore 'fan art' but when you 'sell' a poster of the cool image you made of Batman, Wolverine or Captain Marvel if they see it you'll find yourself getting a cease and desist order.
Now as to 'how' these creators get away with it, is they are small fish in an obscure pond. And if no one is reporting it then it's pretty likely that the copyright holder isn't even going to know about it. Still doesn't make it legal or right.