Firstly.
How the hell are we supposed to know what you are looking at ?
Secondly there is a little test for stuff you see on the web,
If I am making a good product then I will stamp my name in it so everyone knows who made them, will recognise them as being excellent value for money and buy more.
If I am selling total garbage, blades that do not comply with USA standards, blades that are soft and bend easily or go dull spinning in free air or blades made from high carbon steel that shatter if they hit something hard thus potentially injuring people then I will not have any name on them so if the poo hits the fan I can vanish into cyber space thus avoiding any damages I might be liable for.
Thus if they ain't got a brand name on them don't touch them unless you are one of the type who give their kids loaded guns to play with.
If it has got a brand name, google it and if all that comes up is the advertisements you were looking at leave them alone.
FWIW I can not buy blades wholesale for those prices.
factories in CHina work on very small margins, thus there is no such thing as a defective product.
Factories that make parts for foreign companies that do have quality control resell what the factories reject into the aftermarket parts stream.
Thus a lot of what looks too cheap to be true, is just that reject parts.
Next size & weight of a blade is not a guide to quality.
The blades that go on Pro-Riders are very light because they are made from a very high quality steel and fully forged.