firstly if using purely FX lenses on DX, you will never be able to get UWA range.
secondly, FX lenses are more expensive and heavier.
thirdly, DX lenses are cheaper, and if bought used, when upgrading to FX, most people will not lose much money when selling them again. Buying lower end FX lenses will give issues when really moving to a FX body. Since it is lower end, it works ok on DX, but will work badly on FX. So that logic doesn't stand as well. Since when upgraded to FX body, need to get another better performing FX lens and sell the low quality FX lens and it will even a lot harder to sell a low quality FX lens than a DX lens. Seriously speaking, many DX lenses are available now at good pricing with very good edge performance.
Actually it is comparatively easier to sell lower cost DX lenses in BnS nowadays (eg. selling a Tamron 17-50/2.8 vs a Sigma 24-70/2.8 HSM). You may argue that a Nikon 24-70/2.8 is easy to sell. But think, if you are on DX moving to FX, will you sell a 24-70? No. Irregardless of DX or FX lenses, there will be lenses that will sell very well and there will be lenses that will not move. It is pretty much the same DX vs FX.
Personally, I believe in living in the present. With enough research, one can get good quality glass at good prices and good resale value, be it FX or DX lenses.
When time comes when one decides to move to FX, there might be new lenses that work better and replacement models. E.g. VR1 vs VR2. D vs G. So need to buy again anyway. And depreciation is a percentage of total value. And the lower value option will always depreciate less in absolute value compared to the pricier option.
And lets not even go into present value and future value of money.
So if you really factor it in, you do not really lose that much money if you factor it in and have a good buying strategy. FYI, I sold my 35/1.8 with almost no loss after using it for 6 months. But you really need to know how to pull that one off, which I do. And no, I did not sell it overpriced like what many people do in BnS. Sold it at fair value.
So that is why I believe what I said, to compromise and use solely FX lenses on DX bodies is illogical and a waste of money and resources. Should not even think of buying for upgrade progression. Just buy what you need in terms of shooting needs. If buy FX lenses in anticipation, might as well just bite the bullet and get the FX body right away. Will save more money that way, seeing how the thing that depreciates the fastest is the camera body itself.
