On more than one occasion when shopping for stuff in a supermarket, for buying one product I sometimes get a similar product manufactured by a different company, free. Could it be that by giving out that small free sample, the supermarket is trying to get you to switch to buying the other product if you find it's better than the one you bought or is the cost of that product passed onto someone? A small price increment on some product could effectively get back all the money that the freebie cost. Do stores/supermarkets/etc use freebies to make us by buy more from them, and get more money from us?
I'm not sure I have seen what you're referring to. I have seen samples included on full-sizes products before, but it's usually manufactured by the same company. As in, there might be a shampoo that also includes a free sample size of a hair gel. Or a pasta sauce that offers garlic bread, etc. I have never seen a one-to-one sample given where it's two competing products.
Yeah, the only time I've seen this sort of thing they're from the same company, trying to get you to pick up their product instead of their competitors because you think 'Oh hey, I get this thing free if I buy this shampoo'. That and sometimes it'll be 'If you buy this shampoo, we'll knock off two pence off of toilet rolls' but that's the shop themselves trying to make you buy somthing else, rather than the companies.