Shopping Comparison Websites
Bing vs Google Paid Placements

Google Shopping results are paid placements. But some are reporting that even Bing results are paid. Interesting that Bing would launch a campaign without checking to see what they are doing as well, perhaps this is changing and the campaign launched before the adjustments had been made.
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Bing does have a disclaimer on search results for instance on a search for digital cameras, note that “Payment is NOT a factor used to rank search results in Bing.”, which implies that paid search results are included, but the results are not re-sorted based on it being a paid placement, unless you are looking at the ads on the top of the page.

There are other options if you are looking for a balanced check on price comparison:
decide.com
shopsavvy.mobi
sortable.com

For those interested Google in the shopping results shows this message on the right:

Products and offers that match your query. Google is compensated by these merchants. Payment is one of several factors used to rank these results.