I don't think it's such a big deal...Sure it's nice to have a light paddle..but not nessesary...IMO.
It's like buying a bicycle...Let's say a Mt Bike..You can buy an average heavy bike ..or the lightest carbon frame bike...I comes down to what you can afford.
Sure a lighter bike is a bit more fun to ride..but not absolutely necessary to have fun and get fit...I like paddling to keep fit and I used to think that having a light paddle was like drilling holes in the weights at the gym so they are easier to lift.
I've been making my own paddles for years..Alloy with a plastic T grip and a stiff plastic straight blade...They work great...Really great...and cost me only $50 to make.
The problem with some cheap paddles is that the blade is crap..A soft plastic blade will flutter all over the place when paddled hard.
Also..There's nothing wrong with an alloy shaft..The only thing is they can be a bit stiff and may cause joint pain over time..Carbon is a bit more flexy/springy..at least alloy should not brake like carbon can..but it can bend.
When swapping between the Naish carbon and Naish alloy the weight difference seems to be in the blade end..not so much the shaft.
But this extra weight can also be a good thing when learning..You will often swing the paddle to get you balance..You will do it a lot...But when you swing a light carbon paddle there is no weight there and you will probably fall in.
The next thing is the off-set blade (about 10-15 deg)..Most cheap paddles have a straight blade.
An off set blade does three things.
1...it gives greater reach when dipping at the start of the paddling stroke.
2...it gives a more forward push at the power part of the stroke..and is less likely to lift water at the end of the stroke.
3..at the end of the stroke the paddle will lift out of the water easier than a straight blade..It seems to just slip out without a splash.
But even without these three things a straight paddle works great..just not quite as good.
Once the paddle is being pushed through the water the light weight means nothing..Where you do notice it is in the swing weight as you bring the paddle forward or swap sides.
I've been using my home made paddles for more than two years now..and I only have a carbon paddle now because I won it....and I use it all the time now..I love it..but it is a little short.
With a cheap paddle you can treat it rough..drop it..push yourself off rocks..dig it in as you stand on to the board..An expencive carbon paddle needs a cover or bag and baby it more...well I would.
Today I ordered myself a alloy Naish paddle and I intend to take the blade off and mount it on my home made paddle that is the length that I like for flat water paddling..and just use it for long flat water paddling trips..like in the river etc.
Here's a pic of my home made paddle..and a few different shape blades that I have tried.
DJ