Billingsly is in the ballbark of what is fair for a top closer. Billingsly is a low-end #2 or a high-end #3 SP.....just about fair value for Bell.
In theory, you should probably be able to do slightly better.....but just slightly. I would value Bell more like a solid #2 SP.....as opposed to the borderline #2/#3 SP that is Billingsly. But in real life, it doesn't always work out that way....since you need to find somebody else in your league that, a) needs a closer, and b) has a SP of fair value they are willing to part with.
You might want to make sure you can't get a guy like Marcum, Scherzer or Beckett.......but don't waste too much time.....Billingsly is a fair deal.
Your other option is to consider adding a solid hitter to the deal (if you have one to spare) so that you can grab a really high end SP.
help with mine?http://www.fantasybaseballcafe.com/forums/viewtopic.php?t=431897