[MENTION=441228]2lo8[/MENTION], what is the plumbers wrench trick?

Are you saying the higher end chains are not made of harder steel?

Unless a company outright says they use harder steel and their chains last longer, I wouldn't believe it. Most companies will say it's proprietary coating X that increases chain life. I have no intention of trying to test how many miles a coating adds or doesn't add.

The only noticeable jump in coatings I've personally noticed is plated and unplated, because unplated rusts, and they tend to be cheap corner cutting chains.

The trick with the plumber's wrench (really pliers, like channellocks) is to stick the link in the jaws diagonally and press on the corners with the fixed pin and not the slots. It helps to use a paperclip chain hook thing which most people use for joining chains.

Problem with steels are that generally, as steels get harder, they get brittle. You COULD try heat-treating all the pieces of a chain, maybe even case-harden them, but then a chain would cost maybe $100. Coatings and regular lubrication are much more cost-effective.

I've gone to Wippermann stainless chains on two bikes that I ride in the wet and am likely to get particularly dirty, and am really liking the simplicity of maintenance.
Wippermann recommends wax lubes, and the water-based lubes like Pedro's Ice Wax are great.
Hose it down to clean it, let it dry (no flash rush on stainless), reapply the lube.

I do this with just any regular pair of pliers.

You could alloy them to form carbides too, and numerous other things that would most likely increase cost and complicate things with dubious benefit. KMC, SRAM, and Shimano all advertise heat treating of some sort in the product description of at least some of their chains. Heat treatment may be standard on high end chains, or it might not. But I would imagine if it had some sort marketable advantage or was different, they'd advertise it.