Many businesses are run totally by the computer with no personal intervention unless asked for. Shipping for an item less than $5 might be 2.50 (for example) 4 items would be $20.

i once had to order some tiny metric screws for a fencing sword from NY to CT and shipping was something like $12 for 4 tiny little screws less than 1/16 long. I called them and spoke to the office and asked them to put them in a regular business size envelope with a 46 cent stamp and they did. We both laughed at the ridiculousness of shipping an item like that. Matter of fact, they gave them to me.

My point is call them up and have your clamps in one small envelope or whatever.