Emma at Yell.com kindly points out in this comment that Yell.com do publish performance stats online. Not sure what position at Yell Emma holds, but intrigued and pleased that Yell are monitoring the blogosphere.
Now I had a good look through yelldirect.com (their advert management site, where you can view ads, billing history, etc.) trying to find performance stats yesterday, before I called them (and before I made my last post), and I couldn't find them. But I can find them now so either Yell has added this functionality in last 24hrs (possible, though unlikely) or I missed it yesterday (oops).
Nevertheless, the reporting tool is very rudimentary: it can only show one month at a time, and says it updates around the 10th of the following month (though today is the 6th and I can now see Feb data; yesterday when I phoned Feb data was not available, I had to make do with Jan). So it certainly isn't real time, as Emma claims, but is enough to check if the cost-effectiveness of each ad is roughly equivalent to Google, or (as in our case) 10x less cost-effective.
I still don't understand why it is so expensive. I can't believe that any rational competitor would really think it sensible to pay over £7 / click, so does Yell just hope to hoodwink a new advertiser each year? Clearly no-one who has seen their own performance data is going to renew at that cost per click. And any sensible advertiser next year (these Sponsored Listing ads are a new thing) will ask to see how many impressions / clicks a particular category generated the year before, and once they see that data, presumably won't book it?
Yell.com still don't seem to have grasped the fundamental difference between a printed directory and online advertising. With a printed directory, you have to charge a one-off annual fee, as the directory is only printed once a year. There is no good argument for charging an on-line advertiser a one-off annual fee, you will end up undercharging some advertisers and overcharging others (vs what they would be prepared to pay in an efficient market). And given the astronomical cost-per-click of our ad I rather suspect that more people are being "over-charged" (i.e. paying more than would once they know the real value) than "under-charged".
I've just found that they now offer a pay-per-click model, but only for national searches, why don't they just make the whole thing pay-for-performance (either pay-per-click, or given that some people will just call the phone number on the listing and not click through to the website, pay-per-impression)?
Maybe they will. Only way to survive in the long term, in my (loosely informed) opinion. But it shouldn't be about surviving, it should be about prospering. Yell has huge brand awareness and a massive database of local businesses, it should be making more of this inheritance, I rather feel they are slowly squandering it.