Good guns no doubt, but a large .380 will never increase in value like an HK P7 which is the same size, albeit heavier. With Beretta re-releasing the 84/85 series in the U.S., I don't see demand increasing for a large .380 as there are other alternatives, especially ones that are smaller, and lighter.
The "Rolls Royce" of anything will always go up in value. One of the Sig .380s was very light and had an aluminum frame. Suitable for a suit or sportcoat inside jacket pocket. It may have been the older P230 model.