There would be value in this strategy if the mini-sites offered premium services, and appeared to the shopper as an authority in the genre.
I'm considering doing this with one of the product lines I sell. If I go that route, I'd go factory direct rather than through a distributor for the best possible pricing, and make it the go-to site for Acme Widgets in my niche. I've seen other sites in my niche focus on one product line and do very well in terms of sales as well as SE rankings.
I think the operative word here is "authority". You have to be the one that everyone knows has the products, the knowledge of the products, and has great prices, too.