I've purchased a few attenuators from Amazon / BECEN. They are usually OK, with decent performance up to 1GHz (at least the smaller-attenuation 10W SMA connector ones I've got) Sorry, I don't have any test data handy. But one 100W "50dB" N-connector one I got from BCEN actually just has about 40dB attenuation. It was reasonably flat over my frequency range of interest, and it managed to handle the 50W or so I ran through it. I put a "40dB" label on it and still use it.
These attenuators are commonly available from aliexpress.com, and they all look the same -- I don't know who actually makes them, or where "BECEN" gets theirs. QA rejects, perhaps?
So if you are able to test the attenuator before using it, it's probably worth a shot. If you want something with better-guaranteed precision Amazon/BECEN is probably not your best source.
And watch out for power ratings on Chinese attenuators and dummy loads. I can buy the exact SMA dummy load, sold as "1W" and "2W" devices. They get pretty hot at 1W.