I did this a while back, shipped about 50 discs to AT members.
I found some CD mailers that worked out to like 30 cents apiece (self sealing, non-padded - I can probably find where I got them if you want).
Here Part #50PS
Picture
Order # 50 100+ 200+ 600+ 1000+ 5000+ 10000+
50PS $.30 .26 .20 .18 .17 .16 .15
They require more than one stamp to mail, but less than two. I was lazy & just used two, but if you send them all out at the same time you could probably pay exact postage & save money.
Total cost should be <$1.25 including the cost of the CD.
Viper GTS