ah but all grades of stainless steel are not created equal..... any exhaust made from anything other than 304L is not going to last you a significant amount of time.They are stainless and TIG welded, so can't foresee any quality issues!
Whilst it may say 304 (i haven't looked at the adverts) many cheaper outlets will use a far lower grade (some will even use mild steel and then nickle plate it) of stainless steel which has no place on an exhaust system.
Then if it has been TIG welded and NOT back purged then the inside of the welds will be sugared and have embrittlement and fail very quickly. The picture above shows very pretty welds but i'd be curious on the amount of penetration those welds actually have.
Then you need to question the quality of the material within the cats.....
The closer it is to the heat source (the engine, turbo/supercharger) the better the spec it needs to be.
It's cheap for a reason, the materials market on a global scale relies upon certification for proof of materials and to back up CE accreditation and it's why a lot of industry won't buy certain materials from the Chinese domestic market....
just my 2 pence worth