my experience with diamond blades has taught me this. price barely matters. It is all in the manufacturing-steel strength, flux for the diamonds, balancing etc. because we do a lot of precision cutting with stone consistency of the cut is almost as important as speed.
after years trying different blades I still can't say that we use the best blade with the most value to us...but we have narrowed it down. I have spent several hundred ea on supposedly top o the line cats ass blades and found them to be all over the place in terms of quality.
We spend about $100 on blades now and buy about a half dozen at a time. From a company that i won't mention, but is probably one that has harassed all of you in one form or fashion..and these guys are the tamer group of the ruthless diamond blade merchants.
They work great. last a long time and are consistent.
I definetely WOULD NOT line item this unless its a big enough job where this would be substantial enough to show the client a break out cost. which we have never done... i just figure it into my cost of opening shop every day: we use 6 blades times $100 each equals $600 a year which needs to be recovered..and we get it through our labor rate.