The Code

Create a text file called amazon_price.vbs with the following code:

' amazon_price.vbs
' This VBScript prompts for an ASIN, and returns the price.
' Usage: double-click amazon_price.vbs, enter ASIN.

Sub AmazonQuery(ASIN_In)
  Dim SelectedText
  Dim MSXML
  Dim XMLURL
  Dim Loaded
    
  ' Make sure that some text is selected
  If ((Len(ASIN_In) = 0) Or (ASIN_In < " ")) Then
    WScript.Echo "Please enter an ASIN."
    Exit Sub
  End If
  
  ' Set Associate ID and Developer Token
  AffiliateTag = "insert associate tag"
  DeveloperToken = "insert developer token"
  
  ' Create an instance of the MSXML Parser
  Set MSXML = CreateObject("MSXML.DOMDocument")
  
  ' Set MSXML Options
  MSXML.Async = False
  MSXML.preserveWhiteSpace = False
  MSXML.validateOnParse = True
  MSXML.resolveExternals = False
 
  ' Form the request URL
  XMLURL = "http://xml.amazon.com/onca/xml3" + _
           "?t=" + AffiliateTag + _
           "&dev-t=" + DeveloperToken + _
           "&page=1" + _
           "&f=xml" + _
           "&mode=books" + _
           "&type=lite" + _
           "&AsinSearch=" + ASIN_In
  
  ' Issue the request and wait for the response
  Loaded = MSXML.Load(XMLURL)

  ' If the request is loaded successfully, continue
  If (Loaded) Then

    ' Look for the ErrorMsg tag
    Set XMLError = MSXML.SelectNodes("//ErrorMsg")
    
    ' If it exists, display the message and exit
    If XMLError.length > 0 Then
       WScript.Echo MSXML.SelectSingleNode("//ErrorMsg").text
       Exit Sub
    End If

    ' If there's no error, use XPath to get the product name
    ' and the price
    WScript.Echo "The price of " + _
      MSXML.SelectSingleNode("ProductInfo/Details/ProductName").text + _
      " is " + _
      MSXML.SelectSingleNode("ProductInfo/Details/OurPrice").text
  Else
    WScript.Echo "The service is not available."
  End If
    
End Sub

strASIN = InputBox("Please enter a product ASIN.")

AmazonQuery(strASIN)

As you can see, this script looks for two specific pieces of information in the response: the product name and the price. The XPath queries to reach those pieces of info are:

ProductInfo/Details/ProductName
ProductInfo/Details/OurPrice

By changing these paths, you can bring up any other bits of available data.