Phil, owning both (plus the W601 Tigers PC), I can tell you that the W601 Premium is not in the same ballpark as the 1915 Red Sox PC for the reason you stated -- it's not a card. It's also not in the same ballpark as the W601 Tigers PC for that same reason. As for "smarter" buy, the Ruth team PC is a card, and has Ruth's first major league image on it. There's no player who is more important to collectors than Ruth. To compare the 1915 Red Sox PC to the 1905 W601 Tigers Premium is like comparing apples to a fire hydrant. Not even on the same planet.
The better comparison would be the 1915 Red Sox PC to the W601 Tigers PC and for the reasons described above, I'd agree that the Tigers PC featuring Cobb's first image is undervalued. But there's no way it will ever be worth what the 1915 Red Sox PC is worth -- Cobb does not compare to Ruth in the eyes of collectors.
To me, the argument that makes more sense is why the 1915 Red Sox PC is worth so much less than the 1916 M101-5 Ruth cards, especially when you consider the PC is a year earlier and has a way lower population. But as Jay pointed out, the PC doesn't feature Ruth alone, and well, there you have it.
I also lament prices going up but then again, I also decry young people stepping on my lawn. That's how the world works.
