The price difference is usually that one color is being added or continued--the higher priced one-- and the other color is being discontinued. Or the lower priced color isn't selling as well, so it's on sale to move more product.

I have to buy wide width shoes, which many shoe stores don't carry, or they only buy one pair of wide shoes per size, i.e. they may buy 20 pairs of size 7 and one pair of size 7 wide. So I do most of my shoe buying on the internet. It's just like any other store--popular things sell out quickly.

And these days, on-line retailers seem to be carrying less inventory than they did even 5 years ago. I've noticed if I don't buy something right when I see it the first time, if I come back, several sizes and colors will be sold out. Fewer sales, too.

Shoes threads come up often. As we age, we want comfort as well as style. Some of us have had difficulty due to size and width. Me, for example. Small wide foot.
I know your screen name is ms-thrifty, but there sometimes you have to bite the bullet. A comfortable pair of shoes is well worth any price.
My go to places: Aerosole, and Easy Spirit. I check out the shoe departments in Macy's and Lord and Taylor.
There is now a crocs store, although not close to me. I like the sandles and ballet flats.
Macy's in NYC has a whole department dedicated to comfortable shoes, so you can probably get them online.
Check out Walking on a Cloud.com. Some of the shoes cana be expensive, but you if you find something, you might be able to go to Zappos and get it for free shipping.

My experience is similar to camlan. I have wide feet and like platform wedges as I am short and love the height and the stability. I pretty much have only been buying shoes online for the past 8 years. I love being able to search, filter and sort. The reviews on sites like zappos are often detailed and spot on. Free returns help. Incidentally I also reduced my shoe shopping to about 3 pairs a year - a summer flats, a clog or wedge and a pair for work.

If you find a shoe you really like, you can always google the name of the shoe to find other on-line retailers who carry it. There's always the chance it might be on sale, or available in your size/color, at another web site.

I second camlan's suggestion. I have found Zappos shoes on all kinds of online retailers - manufacturer's website, department stores and other online shoe stores like shoebuy and footsmart.