All of our shipments go out USPS International Priority Flat Rate, based on package weight and value. PayPal adds these amounts automatically. I check their rates against another shipping program and pick the cheaper. If the total is less than you paid, I will refund the difference. If it is more than what you paid, I make up the difference. All shipments are insured for full value as I cannot afford to lose any revenue -- my margins are that skinny. Where possible, a signature is required. Typically, to ship a cam and spring set will cost 50USD anywhere in the world. A piston set $85. All these together, still $85 -- it fits in the same size box. Pistons and cylinder about $100, but they fill the box; any additional will bump it to 125USD or more. Due to the USPS's bizarre pricing structure and rules, it is often less costly to send orders in multiple parcels.
The USPS does not play fair. I had a bunch of head and cylinder pairs boxed up in containers marked "USPS Large Flat Rate." I noticed deteriorization on a few boxes and decided to re-box them. I opened a carton marked "Large Flat Rate." They weren't as tall as the boxes I had been using. A pair of heads or cylinders would not fit. They changed the size without notice. I will continue to use the larger, old-style boxes as long as possible (although some of them are looking quite ragged). So, until I run out of large boxes, look for $100 shipping. When they are gone, $150 or there abouts. I wish I could quote less.