I get calls from time to time from ad salesmen who want me to spend $10,000 (or more) in display ads on their sites.

They promise to give me a great deal and they say their site is a great fit for my products, so I ask them if they’ll take the risk and charge me on a cost per acquisition basis?

Of course they aren’t interested in doing that, so I’m stuck with plopping down $10,000 (for which I might get $200 in purchases — if I’m lucky), or just giving up on display ads.

(They’ll also give me the story about how you can’t calculate the value of display ads on a click-to-conversion basis, and that the ads pay for themselves in branding and increased search, etc. I’ll post something on that another day.)

If I don’t want to buy specific real estate on specific sites, I can also run display ads on a network, like Google Adwords. I can even target specific sites on Adwords, which gave me a good idea the other day when a salesman called.

Salesman Joe from mygreatsite.com asks me to spend $10,000, and I go through the old cost per acquisition pitch (just for fun — it never works), and the conversation lags. Joe says “sign up for $10,000, and if it isn’t working after a couple weeks, we’ll cancel it and save the balance.”

That’s a little nicer, I guess. That way I only waste $3,000 and get no revenue at all.

But then I pull out my trump card.

I take a quick look at mygreatsite.com and notice that it runs Google ads, so I set up a site-targeted campaign in Google — text and display — that might cost me a couple hundred bucks. I tell Joe to check back in three weeks and we’ll look at the data. If the Google ads worked, that tells me there might be some hope for selling my products on mygreatsite.com, and I’ll consider the $10,000 gig. But if the Google ads don’t work, it’s not worth the risk.

(Of course I’ll always take the cost per acquisition deal if they’re so sure it’s a great opportunity.)