There are a couple of different ways that you can look at an iron fly: (1) it's a defined risk short straddle; or (2) it's a really tight iron condor. I tend to treat them as "defined risk short straddles," because I manage short straddles differently from short strangles (an iron condor is basically a defined risk short strangle). With short strangles and iron condors, I look to take the whole trade off as a unit at 50% max profit.
Short strangles and iron flies are a different story. If you look at the metrics for this particular trade, the break evens are quite tight: 19.92 and 24.08 -- much tighter than they would be for a short strangle or iron condor setup, and there is virtual certainty that one side or the other will be tested sometime during the trade since the short options are basically at or near current price. As with all premium selling plays, though, you're looking for to contract rolling into expiry, and you can profit from this circumstance even when -- with iron flies or short straddles -- price has broken one of the short strikes of your setup (but not the long side).
As always, there are trade offs with the setup: max profit is a 2.08 credit ($208/contract; BPE $142/contract). I couldn't get near that much credit if I went with a standard iron condor (an April 15 15.5/18.5/25.5/28.5 iron condor will rake in a whopping .41 in credit at the expense of a BPE of $259/contract). Because of this trade off and the fact that the probability of profit for an iron fly is basically a coin flip as compared to the iron condor's 70-75% probability of profit, I'll look to take this setup off at 25% max profit instead of the usual 50%.
Naturally, this isn't my preferred way of doing things. However, with underlyings below $50/share, you generally cannot take in enough premium if you're going with a defined risk arrangement to make it worthwhile unless you tighten your iron condor or go the "defined risk short straddle" or iron fly.