(something that's good value isn't necessarily cheap, but it's a good price considering the quality)

Could you tell us what you are going to describe that in English, ah, British English :P ?

In my thought, you probably want to say 价格合理，价格公道，价格适中,价格合适。All of them can mean some commodities have a good price with the equal quality. They have many variations:
价格挺合理（的），价格还挺合理（的），价格绝对合理，价格非常合理，价格相对合理，价格比较合理，价格还算（是）合理。。。well, I only can think these now, and you may change 合理 to other three words.

If you are a buyer, when you think something is 价格合理的 after you get the quotation from vender, you can tell your friends and say that in your heart: 恩，价格还挺合理的。Don't tell that vender, because you maybe need to bargin. :P

If you do business with some clients, you can say 这个价格还算是合理的，请您考虑一下。

Are there other situations that you want to say it? I only can think of two examples now.