Value is very subjective. To someone who is dying of thirst, water could catch $100/bottle (and, in fact, does with some of the fancier, gourment water), but to someone who just had a full meal with plenty to drink, a gallon of fresh water from the streams of Mt. Ararat wouldn't fetch you a nickel. So, what is the value of good design? For many people the value is very low. They don't understand that good design can = more business. If you mow lawns for a living and have an ugly business card printed at Office Depot or Kinko's you probably won't get the big accounts that someone with a perfected image will.
As a designer I talk to a lot of people who want to do both a website and logo. Logos can take me between 40-50 hours to complete. There is a lot of back-and-forth between myself and the client, and a lot of trying to interpret what they actually want. Websites can often take about the same amount of time, but most people won't pay more than $200 for a logo. They will, however, pay a lot more than that for a website. Of course, this is really all dependent on what type of logo or website someone wants, but more often than not what is simple in their mind is quite complicated to actually complete.
So, how do we determine value? It still goes back to what the client is willing to pay. My job is to get them to understand the value in a good logo or website and what that will translate to in dollars of business. After all, isn't that what every client is after anyways?