Both are luxurious items that you don't have to have. One could argue you can make a much faster car for a third of the cost. But it's not a Ferrari.

At least with the lens you can have the very best 1200mm lens made by anyone. Maybe some do not think it is worth it. But for some (Like me) are willing to pay for it. Good value or not it still is the best. Sure you lose IS, but IS is not a deal breaker on a lens like this. You are buying it for the best IQ at 1200mm and the widest aperture at 1200mm. You are pretty much limited to tripod use, but honestly that is pretty much the only way I shoot at 1200mm and beyond anyway.

Different strokes for different folks.