Road Bike pedals?

I just got a $900 Trek Road Bike and it comes with clip on shoes. There are these aluminum paddles that go between the shoes and the pedals. Shimano had them for $60 and a higher end company sold them for $100. The high end ones were much more lightweight compared to the Shimano ones. Does it pay here to spend the extra $40 or is the extra weight not of much significance?

What matters is the total weight of bike and rider. Acceleration and vertical ascent rate on hills is almost proportional to total weight (at constant power). Total weight really doesn't matter on the flats at steady speed. EG, if you, your clothes, shoes, water and bike now weigh 200 lbs, saving 8 lbs on a new bike will leave your "system" at 192 lbs. That means you'll climb steep hills and accelerate ~4% faster. On a low-speed 10 minute climb, 4% is 24 seconds, which is a few bike lengths advantage.
"Does it really matter?" For most of us non-racers the answer is really no, but lots of us spend big money to get that small advantage. Guess it all depends how badly you want to beat up on your buddies.

Apart from the math, a lighter bike feels "quicker" and more responsive under you. When you step down on a stiff new 16-17 lb wonderbike, it will feel like it's a lot quicker to jump than your old lead sled. Despite what you hear about old-school steel, bet you'll like the ride feel on the lighter bike better too.

Your talking about pedals only. Would you notice a couple oz? No, you wouldn't - but that never prevented anyone from spending big bucks for a little lighter component. The practicallity may not be there but if you have the money and would like the lighter pedals, it's your call. We all make choices between needs and wants everyday.

Reducing rotating weight (i.e., wheels) is much more effective than reducing non-rotating weight (i.e., seatpost). In general, saving weight in the pedals doesn't have a really big payoff, but $40 is not much compared to what you could be spending to make your bike lighter. To me, pedals are a low priority when it comes to shaving rotating grams off my road bike, but YMMV.

The most important thing: will you believe that those lighter weight parts will make you faster? If so, then buy them.

HTH