I think generally over 10,000 is definitely worth a look in if you have the time.
And just because a domain comes up sub-10,000, doesn't mean it's not worth developing either. Some niches are super lucrative, but for whatever reason the big players haven't cottoned on to the idea of online advertising (yet) and the CPC will not reflect the money making potential. If the domain you're thinking of developing refers to a product or service, try to make an estimate on what kind of commissions you could reasonably ask for if you were selling leads.
On the other side of the coin, realise that if the CPC is really high, you'll likely be dealing with a lot more competition, and will have a much harder time ranking.