Know-How Exchange : Research/Metrics

I am looking for research/statistic on the success of sell through as a result of sampling a retail product through hotel personal care amenities. When a retail product licenses their brand for use as hotel amenities - how effective is this in generating increased retail sales? Since there is no cost to the sampling - and often a fee or royalty for use of the brand - this is a very cost efficient way for a retail brand to sample directly to their target audience - but is their proof of sell through? How effective is it in comparison to other sampling or promtional strategies? Looking for stats or research on this subject. Thanks

C. Guy