Do you want to make money on an excessive move, or on IV shift? If the first, I would buy straddles, not strangles. If you expect less movement then IV predicts, sell strangles. Anyway, 30 can be cheap, or expensive. I've seen IV of 6... and it was still expensive... 50 was cheap... It's all relative....
Pretty well the same post as mine, but worded differently. And you're right, it's all relative ....... to the underlying.