Sure it would, but that could be said about any purchase off coinbase - they eat into your profit margins.
I believe the way this one works is it takes the sum of your monthly change and then invests into monthly. This way you're not paying 2$ on a 50cent transaction. I also think it wise to use a cheaper transaction coin than btc, say LTC (or any of the 3 besides btc really). And if you really want bitcoin go ahead and convert it on an exchange, it will be cheaper doing that with small amounts than just outright buying bitcoin.
-best