It seems that with the lower SBD/Steem price that I basically broke even after curation. That's not a big deal I guess. It gains exposure and followers. But when the prices are higher, it basically is more like 10% more than I paid once I factor in the higher value of Steem to SBD.

Edit: My last calculation was from using Smartsteem actually. I just used Minnowbooster on my newest post and it works out to a 10% ROI. Basically you get your SBD back plus some Steem Power. But keep in mind, this might be lower if you haven't made the whitelist yet.