You people crack me up.
Ruffly 20 years ago my 2e Players Handbook cost me $20 at Walden’s Books.  That was for a horribly bound book with no color, bad art, and very very little text per page.
http://www.measuringworth.com/calculators/uscompare/result.php
In 2006, $20.00 from 1988 is worth:
$34.08 	using the Consumer Price Index
$30.80 	using the GDP deflator
$0.00 	using the value of consumer bundle
$34.83 	using the unskilled wage
$42.26 	using the nominal GDP per capita
$51.71 	using the relative share of GDP
According to that page $35 is about right for that OLD book.  The new editions have been so much nicer in every single aspect that I would pay at least 10% over that if not 30. 
Just go mow lawns for the summer to pay for it… that’s what I did when I was 10.