Fetching Amazon buyback ("trade-in") price

Is there a way to get the Amazon buyback (aka "trade-in") prices for textbooks through an API? I've searched around for a while but can't find a clue how people are getting this for their websites..

Here is the Amazon BuyBack program: amazon.com/buyback

Here is an example buyback URL: http://www.amazon.com/gp/search/s/ref=tradeinavs?url开发者_StackOverflow中文版=rh%3Dn%3A2205237011%26i%3Dtextbooks-tradein&field-keywords=978-0321614018&Go.x=10&Go.y=17

I'm aware that I could just fetch the pages and parse the HTML, but if there is some way to get it through an API or whatever, I'm sure Amazon would prefer that to just parsing the page (also it would be faster to query).

The Product Advertising API has it in the ItemAttributes section when you do an ItemLookup search, as shown by this sample call (I believe this is perl, but just to show you a sample):

my $request = {
Service => 'AWSECommerceService',
Operation => 'ItemLookup',
Version=>'2010-11-01',
ItemId => $itemId,
ResponseGroup => 'ItemAttributes',
};

snip
'ASIN' => '0136100570',
'ItemAttributes' => {
'NumberOfItems' => '1',
'IsEligibleForTradeIn' => '1',
'TradeInValue' => {
'Amount' => '3550',
'CurrencyCode' => 'USD',
'FormattedPrice' => '$35.50'
},
'ListPrice' => {
'Amount' => '18900',
'CurrencyCode' => 'USD',
'FormattedPrice' => '$189.00'

Source: https://forums.aws.amazon.com/message.jspa?messageID=212679