Depends on the directory and your business model. Some business models can make millions of dollars off of one conversion, some less than a dollar. And I would ask yourself how much traffic you receive from the standard listing first. If it's a decent amount of traffic and your business model supports it, I would give it a try.
Advertising is a funny thing. I've learned that the only way to know whether an ad will work or not is to run it. If you try to judge how one ad will work based on how another worked, you risk getting it wrong and missing out on some great results.
If a cheap ad does well, then is an expensive ad from the same website/publication going to do much better? Maybe. Maybe not. There are so many factors and variables that may influence how well an ad works that trying to make predictions is very chancey.
It's a matter of reaching the right person at the right time with the right message. Just because one ad performed a certain way, you can't assume that a different ad, elsewhere, or at another time, will do better or worse.
Try it for long enough to give it time to work and come back and tell us what you learned.