As mentioned previously in this thread (although not quoted), those compose of perhaps 10% of the price, or approximately $40. Why wait around or hang your hopes on getting an upgrade kit to save $40? Not to mention an old S1 is worth about $150 or so on the open market, and you lose the ability to sell it if you upgrade.
That's your estimate. But why do you think that? Shipping alone must be non-negligible, as Bitmain ships super-fast from China. 4xS3 Blades, could easily fit in a single S3 sized box and weigh considerably less.
Regardless, the real evidence is, Bitmain keeps saying they are going to do it. What reason could they possibly have to tell potential customers that an upgrade is coming if it is not economical for them to do so. Surely they don't want to prevent people from ordering entire S3's if they aren't planning to sell the upgrade. Because it is very obvious that some people who would otherwise purchase S3's are waiting for upgrade kits.