I've invested in a few bottles of 2003's at around $80, but to be honest, I've stopped because I've realized that I can spend $20-50 more now to get my hands on a nice 63/66/70 VP without the hassle of storing/caring for it for 30-40 years. Even the highest-price bottles are only going for $200-300 (not that I have that much to spend on one bottle

So, obviously investing into VP's doesn't even remotely yield the average return on the total stock market (killing the financial investment argument) -- especially factoring in inflation onto the original purchase price of the ports. Old VP's can be had for very reasonable prices in comparison to current young VP's.
Beyond pride of the cellar, port fanaticism, or sentimental reasons, why are people investing by cases into VP's en primeur?