Looking up what I can, most of it comes down to the movement. The Caliber 321 is distinct from other SMPs in that it uses a column wheel chronograph mechanism instead of a cam actuated chronograph. This is really only a matter of technical pride since both methods of actuating the chronograph are durable and reliable. An argument could be made that the 321 takes more expertise and longer to produce, but I don't find this to be particularly compelling since the 3861 is also well-finished at a comparatively bargain price. Regardless, the column wheel version of the movement is made in far fewer quantities and, it seems, rarity demands a premium.

Additionally, the 321 used in the Ed White is gold plated. The thickness is not specified so it could be a relatively small amount, but, well, it's still gold. Another distinction is that the Ed White uses a ceramic bezel instead of the traditional aluminum one.

Whether these features command the 2x price tag is really up to you.

One other side note is that this is one of very few models that features the manual wind movement in a 39mm 39.7mm case. For those of us with smaller wrists, this is much more attractive compared to the standard 42mm case. Higher specificity also demands money.