Agreed. Pretty much everything you buy directly from a Chinese company will be far cheaper. I sometimes buy things on AliExpress.
The tradeoffs are that it takes 1~3 months for things to arrive, you have no return privilege, if there is a problem you are out of luck, etc. For electrical appliances you will probably not have a real UL or ETL listing, and the products will sometimes not meet US safety or materials standards.
But bypassing the entire American retail system is absolutely cheaper if these limitations are OK with you.
The set you referenced looks like a good deal and is from Amazon, so it doesn’t have many of these problems. I mostly need filters. The roller brush is fine on my unit and the little whirling brush doesn’
t seem to actually do anything except entangle.
Mine has a few cracks too. Mine are probably from minute nail-pops on transition thresholds between hardwood/carpeted and hardwood/tiled rooms. Going to countersink the nail heads before swapping out the brush next month.
