Amazon usually gives the cheapest price but it is a weird beast. It does this funky dynamic pricing based on demand (which can be items bought or even page views) and also there is sold by Amazon and fulfilled by Amazon.
Consider this bike which is *sold* by Amazon:
http://www.amazon.com/Diamondback-Bi...+podium+junior
I bought one for $281 about 8 months ago. But directly after Christmas it spiked to to nearly full price $500 and now has dropped down to $385 and sometimes dips down to $250 and upto $400. Unfortunately there is no way to put price watches on Amazon products as far as I know.
Now consider these shoes I just bought which is *fulfilled* by Amazon (another company is the seller).
http://www.amazon.com/gp/product/B00...ilpage_o01_s01
The price varies by shoe size.
but at CC its all the same price regardless of size.
Shimano SH-R065 Cycling Shoes - Men's | Competitive Cyclist