I had the same issue with a domain held by a company that bought and parked domains in the USA. I approached them (and dealt with a woman) she said they wanted $1800 for the domain and said others were interested (yeah right). I walked away. I had the .co.uk and .net versions anyway (but really wanted the .com).
Two years later I knocked back on the door using a different email address. I offered $200 thinking they'd turn it down; I got it.
I've been on the other side of the fence a few times selling a domain also. You can almost smell the desperation in people when it comes to domain names because people get so set on a domain (from experience on both sides of the fence). I think ultimately you've got to be prepared to walk away, it's just a name at the end of the day and there are so many alternatives you could use in the meantime. A domain name isn't going to make or break your business.
I'd drop them an email asking if they have plans to use the domain as it appears they aren't using it at the moment (don't say you know they've been using it on off for the past few years because I'd immediately realise you're keeping an eye on it). Ask if they'd be willing to sell the domain as it's one of a few names you're looking at and what price they'd be willing to relinquish it for.
When they come back with a silly figure, go back and say I was thinking more of $X, then point out you won't mess them around you can have them paid within a few hours via Paypal - trust me it makes a difference to know you can seal a deal and have cash in your account within an hour. If they refuse your offer or don't budge, drop them an email back and say you're going to look at some of the other domains instead as it's just too high a figure that they want but if they change their minds at any point in the future to drop you a line.
You might wait 6 months or a year, or two, but it's better than overpaying, especially if you have an alternative (say .net) to use in the meantime. If they come to sell you'll be the first person they'll try and if they aren't going to use it seriously the prospect of cashing in will always rattle in their heads - especially when they need a little bit of cash.
Good luck. Let me know how you get on.
I disagree with using a woman for negotiations BTW.