Maybe he'll send you a refund for the difference after he deducts his time to locate and inspect the parts (don't want to sell a fellow Rocket Captain any damaged parts), scrounge or buy the packing material to ensure the parts are wrapped to prevent damage during shipping, find the right size box, pack everything carefully then tape it shut (have you seen the price for a roll of packing tape lately?), print out a label and tape it to the box securely, drive to the post office (gas is really cheap these days, hopefully he only burned a gallon or two), pay for the actual shipping (which you already have the price for), drive home, and send a PM or email to let you know the box is on its way. He probably only sank an hour or two of his time to complete this sale....what's minimum wage these days, maybe $7.20/hour?
Good luck with the parts....hope you don't have to spend any more money to get these fitted.
Let us know if we can do you any more favors in the future since we all know how grateful and respectful you can be......