Cadet Chuck:
I think the main reason for the cost increases on kits is because plastic is made from petroleum products, and you know what's been going on in that market lately! And the cost of a barrel of crude is now rising steadily because of the unrest in the Mid-East- again!
Actually many mfrs will tell you that the plastic is cheap compared to the price of paper to make and print the boxes the kits are packaged in.
Tooling costs is the major cost at producing a kit. Transportation is another.
As a mfr I see the cost of shipping which increased again this year and will increase again as gas prices continue to rise. Carriers pass along fuel surcharges which make an otherwise affordable shipping fee, beyond acceptable for those already on a tight purchasing budget. It is a cost that has to be passed on to the consumer as there is less margin in the products themselves to absorb it.