Its all 100000's of diff companies selling the items... aliexpress is just the website.
I've bought heaps of stuff and never had any issues (except with the quality). They are usually quite helpful and will do whatever you ask.. e.g if you have to pay import tax on a certain amount they will usually write what ever amount you asked them to... Again it depends on the company, but I've used a tonne of diff companies off the site and never had an issue.
Just be aware.. the quality is usually.. well.. chinese knock off quality..
I bought some 1W wifi amplifiers and they definitely are not 1W... They look exactly the same as the proper ones, but just don't perform as well.
Same with some laser points I got... meant to be 2000mw but I would say they are on par with some of the 50-100mw lasers pointers I have.
You get what you pay for basically...
Its the same items you get on ebay, but aliexpress (or alibaba) lets you buy in bulk and negotiate on price.
I'm pretty sure if you see any DJI items for sale, they will be copies... atleast from 99% of the sellers.