Just like white diamonds, yellow diamonds have a wide range of color. The yellow tint is even visible in white diamond. Anyone who is familiar with white diamond color chart can tell that color K onward the tint of yellow starts to become prominent. By the time it reaches Y-Z on the chart, yellow color is glaringly obvious. Yellow diamond color range is just an extension to this chart. Beyond the Y-Z shade comes (in the order of increasing intensity) Fancy Light Yellow, Fancy Yellow, Fancy Intense Yellow and Fancy Vivid Yellow. 

As far as the prices are concerned, the price per carat of Fancy Light Yellow for a 1 carat diamond is 20% more than Y-Z. The Price of Fancy Yellow diamond is 25-50% more than Fancy Light Yellow. The price per carat of Fancy Intense Yellow is 30-50% more than Fancy Yellow Diamond. The price of Fancy Vivid Yellow Diamond is 50-100% more than Fancy Intense Yellow. 

To put things into perspective:

A 1 carat weight Y-Z diamond costs around $2000-$2500.
A 1 carat weight Fancy Intense Yellow diamond (Canary Diamond) costs between $5000-$7000.  

The large range in prices are due to other factors like clarity grade, color intensity and presence of secondary hue. Ultimately, the overall attractiveness of a diamond is what makes it sell.