Honestly, I am not believe good chemicals with this price...
It's true that many raw chemicals are very cheap in mainland China or India; but based on my personal experience, I think you should at least choose products that cost $5 per 100g in a black plastic bottle with the AR, Analytical Reagent mark, or for serious applications, choose Macklin products that will cost $7 per 100g, which at least come in a light-proof glass bottle. I can see someone sell 1kg with just $15, but I just rather spend a little more money than take risks.
And get some truly reliable products as a reference, such as Aladdin reagent that costs $10 per 100g or the more trustworthy Sigma Aldrich chemicals, comparing each batch of cheaper products under the assumption that they might not work($5 per 100g or less, what can I say?).