It really depends at the moment, I think it will probably cost you a little bit:
1 SBD = 5 STEEM
So yeah, It'll cost about 0.264 STEEM per 1 SBD you buy and convert, which is quite costly so I'll understand if you don't want to do it. I think I'm losing 50 STEEM on my conversion, but because they've taken off decimals it may be a little better than that. (5.019 I have just calculated from an actual convert)
yeah so it's a loss, probably should put it in the post