We have a huge inventory of 2-3" thick foam board sheets available. They are selling for $1/sq. ft. but open to making a bulk deal ($0.75/sq ft) if large quantities are purchased. Larger sheets are roughly 51.25" x 31" making them $11/sheet and we have strips as well are approximately 15.5" wide x 51.5" making them $5.50/strip.
Note we are unsure what exact type of foam this is. Buyers must verify it works upon purchase for their needs whether to make forms or otherwise.