Maybe if its a F1 car with its $20K clutch and $100k transmission and one has the learning curve of a gnat. Sorry couldn't resist, the analogy needs a little work.
I think if someone already has a good eye, is a quick study, it's fruitless to buy something you'll outgrow in less than a year or two.
Please show me even 50 pictures taken with the D300 that couldn't be taken with a D80 in the first year in the normal course of image making- that is not specifically going out to take a shot that exploits a D300 feature just to exploit it. Seriously, 50 images isn't that much for the difference in price, but I'd love to see them.
Frankly, I'd love to see you make the case for general-purpose photography that someone will "outgrow" a D40 in a year- *especially* if you're a good photographer where the camera body will matter even less than a "beginner's" camera's features do to a beginner's photos.
As far as two hours goes, it's the "smoother" part that's the issue- especially if you're not using synchronized gears and you don't live in a relatively flat location. I think I probably know two people who haven't stalled out a car or ground the gears after two hours of driving at 16. Funny how most driver's ed programs use automatics if it's just a matter of a couple of one hour lessons, isn't it?
Anyway, I'll be eagerly awaiting those "I'd have outgrown a D80 shots."
While you're at it, how about throwing in a few "I'd outgrow a D2x" shots too- since the D300 is "superior" to a D2x, and maybe I'll rent the same lens and see how much the same sort of shot would have sucked if you'd shot it with a D2x.
Note that outgrow means really outgrow, not just pick a scenario where you "need" an ISO or frame rate that's outside of the camera- that's not growth- we could show the same issues with a D3 vs a D300 in that case.
Hey, let's just set the bar at the D40, so we don't have to wait a year, ok? I can borrow one to see if you're right- so let's stick to situations which are relatively common. That should be fun- and I'll have to prove my case- which seems fair given your skepticism. Surely you'll agree that if you can outgrow a D80 in a year it shouldn't take you more than 90 days to outgrow a measly D40?
As far as expense, no- it's pretty commonly accepted that an expense is an expense regardless of income level. The impact of the expense, unless it exceeds income also isn't really at play in terms of pain- it's how that expense relates to income and all other expenses that delineates "pain."
It's pretty basic accounting, but I can draw it out if it's not obvious to you.
Warren Buffet can afford a $300M loss, that wouldn't make him smart for taking one. You can buy a Porsche for driving two blocks to the grocery store every Thursday too- that still doesn't make it a good purchase decision unless you're pretty shallow (even then it doesn't, but you'll feel like it is.)
For what it's worth, the SB800 has an SU-4 mode that will let it flash trigger with any strobe in existence (with any pre-flash disabled for obvious reasons,) so unless you're in a place with a bunch of other photographers, you can just set your flashes manually and they'll work together too, no idiot mode necessary. I tend to use Su4 mode in the studio if I need another small light or if I'm looking to blow out a background doing high key work and I don't feel like setting up more strobes.
CLS is mostly overrated, but if you're going to use Nikon flashes, depending on what you're looking for- you're better off with CLS over PWs, since you lose the only benefit for photographers who know how to light that CLS brings to the table over any other triggering system- FP High Speed Sync. On the D300 that'd get you up a third of a stop before you start to lose flash power to strobing and give the strobing option for higher speeds.
