Do you own a pedal wrench? If you do, you can install the pedals yourself. On the other hand, I am all in favor of supporting your LBS. My last couple of sets of SPD pedals I bought online as I couldn't justify the cost of buying from the LBS. I got two sets of SPD pedals (one for myself and one for my wife's bike) for less than one set at my LBS.

There are things I am OK paying a markup at the LBS, like new rims, as I trust their wheel building skills over mine. More or less the same for cassettes, though I should learn how to remove a cassette from a freehub body. Other items, like bells or brake pads are small expense items where the savings in absolute dollars is small so it makes sense to give the LBS the business.

For some reason, pedals are really marked up, price wise at the LBS. So in a nutshell, since I own a pedal wrench and grease, and can install cleats in shoes, it is hard to say what value the LBS adds in that case.