$250 don't automatically mean significant difference...that's just the pricing policy of Apple.
No, that's the pricing policy of Intel.
Well given how much they charge for extra RAM, it is probably a bad idea to take it for granted that they are only charging the same difference as Intel do for these chips.
Its not as bad as their RAM pricing, I'll grant you that, but it seems a given that Apple will be making at least some profit from the upgrade (not that I would claim they should not).
Yep, and as you say, they're rightly doing so. I think we can establish, then, that the huge price difference between the two processors is largely due to Intel's policy, not Apple's.
http://ark.intel.com/compare/53476,53474
Intel's recommended customer price for the 2.5GHz and 2.4GHz differ 190 dollars. Add to that the cost of actually soldering the thing in the logic board, and you're soon approaching that 250 dollars Apple charges you. I think this price is quite reasonable, unlike Apple's insane RAM pricing.
There is no difference in cost to solder the thing to the logic board, Apple has to solder all the CPUs to the logic board. This is the usual price difference in the actual component cost + Apple's markup.
0.1 GHZ, and additional 2 MB L3 cache.
High end CPUs are usually quite a bit more expensive than the slightly less powerful models. Whether that's worth $250 for you I don't know.