I get a bunch from tricerasoft's site.
Buy the 100 song packages and the price goes down to $1 a song for all of the manus they have, including about half of Zoom's catalogue. Unfortunately I only got as far as "G" on the first 200 songs I bought from them....
That means they probably will eventually get at least another $500 from me.
http://www.tricerasoft.com/karaoke_songs/songs.html
The Mycdg is also a good deal for the sunfly songs ($20). I have bought 6 of their disks and am quite happy with the result. Unfortunately they appear to only have a partial selection of the sunfly songs made.
Unfortunately many of the manus don't do discount burns. I have yet to see soundchoice going for less than about $4 or $5 a song. Even though I have about half my songs from soundchoice, I have not bitten the bullet and bought any custom cds yet from them, mainly because If they have a song I want I generally buy the disk at those prices for the burns. I may need to for a few out of print disks though. My plan has been to base my songlist on soundchoice and fill in gaps by buying burns from other manus. If you try to just buy cds from all of the manus you will end up with lots of duplicates, but even so it is often cheaper that way per song than going the custom burn route.
On the other hand there seems to be a few places that are certainly illegal that charge unreasonably low rates. They seem to fly by night and are gone within a few months of them opening. As for them you are not only pirateing you are giving money to a slimeball crook. MyCDG and Tricerasoft appear legit.
The biggest problem with legit karaoke is the cost of obtaining songs. Often the best route is to buy the big multi song packages such as "Supercore" and even if you only want 10% of the songs the prices are still competitive. Even SGB has about 10-20% good songs. At the going prices they are cheaper than going to custom cds.
Now you may want to not have some of the other songs from a pack on your book, but hey you can always not list a few of them. I thought about it, but eventually decided to list everything I actually own.
THe best thing to do is to talk to your singers and find what they want to sing. Spending money on a song that will never get sung is sad but necessary. At 1 night a week you will probably have less than 2500 songs sung in a year, and it would be expected that after duplicates are counted only 800 or so unique songs are sung. I bought a cd for $65 from SBI for 14 songs, but a lot of them were requests or hard to find "good" songs. I probably was as good or better a buy for me than the supercore set of 350 or so songs.
If you are into indie rock, you are probably best to pay close attention to the British manus, SBI, Zoom and Sunfly.