Having to pay to get into directories means being even more careful about making that submission.
Free is really a thing of the past, and looking at the following is the key to whether you waste money or get a good listing that returns many times over what you paid. I don't think enough background research is done on directories, I mean who is this lot that you're about to spend tons of cash with. They might be a very trustworthy lot, then again they might be a bunch of sharks...
Exactly who is behind this directory
1. Who owns it? - Sole trader, Partnership. Can they be contacted? etc
2. How established is it?
What services does it offer
1. Are these services noticable by viewers? - If you advertise, can you be found easily?
2. Services unique in any way?
Check those rankings
1. What's it's Alexa Rank/Google PR?
2. Where does it's bulk of traffic come from?
3. Do they even advertise?
Has it been professionally designed?
1. Does it look cheap? Chances are if it does, then it's a high risk. Directories that have been invested in, are visited more often, should have better tools, ad services and probably better information.
2. If it looks expensive and in depth, then that could be a sign of the company's disposable income. Who know how much cash any company has, but I'd bet on the more professional looking site having more operating capital any day.
Size of directory/company
1. Are they part of another group? Have more sites/Network?
2. Plans for expansion at all? Mergers or interested investors?
Check for a Press Release
Check those newspapers, mags and especially on the site itself.
If you can't find a Press Release, it could be that you aren't actually dealing with a good company, if they can't afford £200 to have one written and distributed, then I'd avoid, as the site's goal can't be that serious or in your best interests, and if I'm about to put my site in their hands, I want to know exactly how they will drive traffic to my site. Also, unclear info about their ad campaigns is a sure sign of cowboys at work.
Test them. If they don't deliver within 3 months, pull your site from them and use the cash elsewhere.
So many people don't know what they are doing, and these simple checks can discover much - and save you loads of cash!