G10 from MSC Industrial supply is $106 for 4 square feet, 3/8 thick...
www.mscdirect.com
$38 for one square foot, $66 for 2 square feet....
The 3/8 thickness is perfect for carb blocks..I have used it for many years...It can be machined just like aluminum, but is more abrasive and is very hard on common high speed steel end mills and drills..I use cobalt drill bits and carbide end mills for longer life....It's best cut with a Makita 4 inch disc grinder, it eats bandsaw blades....