Satchmo has flexible pricing that allows you to price at multiple levels.
You can create top-level Products, which are the things your customers see on the website. (Ex: Python Rocks shirt in demo store) Additionally, these products can have options (Ex: sizes, colors, etc). The product has a variation for each combination of options. This can be used to track inventory of particular product variations. (Ex: The Large, Blue, Python Rocks Shirt)
Effectively it works like: Product + Option = Variation
The price code looks through these backwards. If the variation has a price then that is used Otherwise the Product price is used +/- the adjustment for the chosen options (IE: XL shirts are +$1.00)
With this capability, you can quickly price a simple store by just using the product prices, and possibly adding price adjustments for specific options, but you have the option of very fine-grained price control by setting prices for each variation.
On the product variations, the price can have an expiration date and/or a quantity. If either of these fields are set then that price is only effective for orders placed before that date, or >= that quantity. The most specific of these gets highest priority (IE: the soonest expiration date, and the highest applicable quantity). This useful for running temporary promotions that automatically expire.