If there was any reason to believe they wouldn’t be selling data anyways, making it a paid thing would make it seem more trustworthy, at least. If it’s free, then you have to assume it’s generating profit through other means.

Though even if that means of profit is from people using it to make Amazon orders, I still don’t trust it because most of the time when I do order something on Amazon, I need to look through a bunch of sketchy results to find one that looks trustworthy. I wouldn’t trust a voice assistant to pick a better option, in fact I wouldn’t be surprised if the voice assistant is specifically designed to select inventory they have more trouble moving.