ORIGINAL: Montague
Did you account for the flute direction when you say 19x48, the flutes are in the 48" direction?
Remember that you need do pieces to total up to a 4x8foot sheet.
I just did a run on their website. White, 2mm coro, 1 4x8foot sheet cut in to 4 24x48 parts. You can trim down to 19" on your own easily enough.
Total, including cutting charges and shipping to maryland is $19.26. Less than twenty bucks. Pricy for a single sheet, but it goes down if you get many sheets at a time.
Checkout should look like this:
I took one sheet and specified cutting it to 12x24, 16 pieces. It calculates over $120 shipping to Texas. Here is a screen shot of the shopping cart. Whatever I did wrong must be the same issue the original poster is having.