Sigh. There's no way they're getting a 50w out of a single diode. 50w is what our co2 laser is at our hackerspace, and requires a 1.5' tube, specialized PSU and watercooling.
These pictures look like the 2w and 2.5w variants on Aliexpress.
Yeah, sites like that are pretty much in the sweet spot of uselessness - lasers too powerful to use as laser pointers, too low quality optics to use for engraving or other laser CNC projects, too cheap to actually deliver the rated power, and too outside the law to give a fuck about false advertising.
There are less-sketchy looking offerings in the 7W range for a similar form factor, though - see [0]. Of course, I'm still not sure if there's such a thing as a 'reputable' site in that segment...
These pictures look like the 2w and 2.5w variants on Aliexpress.