Come on...

Megaup is a file sharing site. Unless you have a paid account, it will be somewhat slow anyway. Also youtube dont allow direct download anymore. Any download from youtube will be done to a remote server of the app you are using, converted and downloaded from the remote server that did the conversion. Again, their bandwidth will be limited unless you paid for premium service.

Since you are getting 30MB/s from Steam, then you should already have a good idea that its not your network or browser problem, but more of a site/server related problem.