Yeah, I didn't want to say ALL purchased lists are bad. I've had a few good experiences buying leads (mostly from CPA offer owners directly). However, I've had FAR more bad experiences, such that I just don't bother with it anymore.
One thing to keep in mind, if you absolutely must buy leads: When it comes to leads, you get what you pay for.
If someone offers to sell you a million records for $100, it's probably about the same as taking that $100 and throwing it on the fire.
I wouldn't really give much thought to anything under 10 cents per lead, and even those will probably only be inquiry leads. It's been awhile since I bought buyers, but last time I bought good ones, they ran about 40 cents per lead.
In the long run, you'll get MUCH better performance by building your own. It takes time, but you'll reap the benefits of an active list that recognizes your brand of communication and is expecting your emails. That can translate well into lots of $$$.