What's the difference between cheap athletic shoes and expensive ones?

I’m not really talking about $20 ones you get at walmart, but lets say Nike running shoes that are in the $40-60 range vs Nikes that cost $100+. Are the expensive ones worth it?

Well from your example it would be a difference of $40-$60, when you add tax a bit more.

It appears that some radically new shoes are coming out now, I have no idea if they do anything but cost more, but they seem to be based on 2 things:
1 - material minimization - from hiking they say a pound on the foot is the same as about 5 lbs on the back, so if you can cut down on weight it would seem to help.
2 - energy return - shoes acting more like springs then shock absorbers, so that energy can be returned to the user instead of dissipated as heat.

I have no idea if the above is true or if they work, and they seem like they might wear out faster.

Also there is the marketing aspect, they want to differentiate their product, and they need high $ shoes people will buy, while still selling to people who will only spend $40-$60.

I’ve been running for over 10 years. FWIW, I wear $14 Wal-Mart running shoes. They work fine for me. Are they the best? Probably not. But they suffice.

I have noticed that the cheaper athletic shoes I sometimes buy almost always start falling apart quicker than the ones I spend a little more money on… The stitching often comes apart and the back part of the shoe (the part that sits behind your heel) has gone to crap (for me) quicker. YMMV.

Durability: Seems hit and miss. I’ve worn expensive Nikes that fell apart just as quickly as cheap Walmart ones, but then, the expensive ones were probably made in the same plant as the cheap ones. My current set of expensive New Balance runners (made in the US, nacht!) have held up better than the cheap ones, but not really enough to justify the 5 fold price difference.

The one feature that I would pay NB for is the fact that their sizing scale has figures for both length and width, something that no other maker I know of does. This does make a difference in fit, I find.

Other than that, as long as the fit is good, I wouldn’t pay more for the name brands. I wear prescription orthotic insoles, FWIW.

Some are expensive for marketing and fashion, some are expensive because of what they do. Lots of those dark-and light soles are different density rubber and the placement influences how your feet pronate, supinate or stabilize when you hit ground. Firmer usually = darker, softer =lighter. Factor in widths, and shapes of soles (some are ovals, many curve in) and you will find the price of those New Balance or Brooks gets you a very precise instrument, whether it is for high level athletics, or used to correct orthopedic problems in a more sedentary population. You can control the position of the foot from from to back, side to side and influence where, when and how force travels through the foot and ankle, all the way to hip and back. See them little old ladies in fugly new running shoes? I help convince them to do that. They are happy, because now their feet do not hurt.