You know the holidays are coming when shopping engines across the web unveil a seasonal increase in their cost per click (CPC) rates, and sites like ComparisonEngines.com argue on the behalf of merchants that not every category should be hit with the same seasonal increase. Countering increased rates on Google Adwords and Yahoo! Search Marketing, the shopping engines argue that they’re just trying to cover their costs, and that conversion rates increase during the holidays. Merchants shouldn’t mind, right?

Not everyone, however, experiences this windfall… making the flat, 25% increases on NexTag, Shopzilla, and PriceGrabber seem like nothing more than a way to exploit eCommerce retailers desperate for holiday conversions. It seems to me that instead of coming off as a seasonal inconvenience, it appears to merchants that shopping engines are trying to take advantage of them. As Brian argues,

I’m not so sure that this Forklift seller is going to see a huge spike in conversion. Or that people will be adding projection mounts to their holiday wish lists. NexTag, Shopzilla, and PriceGrabber are saying that CPC rates increase for them during the holiday shopping season. Again, I don’t think that argument holds for across all product categories. Do bids for textbooks on Adwords or YSM really increase 25%?

Shopping.com, on the other hand, has decided this holiday season to use a variable rate increase from 10%-25% depending on the product. Office equipment and cars, for example, are not usually categories where merchants are wrestling for prominence during the holiday - thus, they’re only seeing a 10% increase. Flowers and items for children, on the other hand, are seeing the conventional 25% as more merchants compete for the clicks.

Shopping.com has admitted that not all categories see cost increases during the holiday season… so why do the other prominent shopping engines insist on these flat increases in CPC rates? It’s an unfair practice, and it shouldn’t continue for this, or any holiday season. Check out all of Shopping.com’s holiday rates and a more in-depth analysis here, and let us know what you think about this flat rate vs. variable rate debate in the comments.