I'm not sure who's got the best deal, but you can check out these websites and see what you think.
http://www.shop.silkwormwholesale.com/
http://www.coastalsilkworms.com
http://www.mulberryfarms.com/
I use wormman.com for my crickets. He charges about $20 for 1000 crickets shipping included and has smaller bundles too. I have been really happy with him and he's in Michigan.
I believe that it takes about 2 weeks for them to hatch. Just watch out if two of them mate. They stay stuck together for several hours, but then the female runs all over the place laying eggs. I didn't have a top on my container because I've never had any get out and she made a mess with them.