I got them all on sale for $2.50.
Lair of the Shadow Broker is huge, great and orgasmic. Would have paid full price.
Kasumi is worth $2.50, but $7.50?! In the words of random black guy from Black Dog, "AW HELL NAW". However, I use Kasumi in my main party along with Garrus. so I guess it might be worth it.
Overlord is lame. The new vehicle is sweet, but I didn't like the actual mission. That British guy was a cunt.
edit: http://www.trueachievements.com/n2630/more-mass-effect-2-dlc-on-the-way.htm