I'm also going through this frustrating choice process...
On the paper front, I originally thought rolls could save me $, but it seems the roll is about convenience and size, not $ (see my thread here
On the ink front, the iPF5000 ships with about $330 more in ink than the B9180.
Taking this into account and ignoring roll paper, the math looks like (Canadian dollars):
Price diff between iPF5000 and B9180 (includes CDN taxes, shipping, brokers' fees, etc):
$2392.62 - $911.99 = $1480.64
Reduce by value of ink that Canon provides over and above HP's starter amount:
$1480.64 - $334.80 =$1145.84
Savings at print time:
Assuming same paper (11x17) and using the numbers quoted earlier in this thread ($0.25 per print on iPF5000 and $1.80 per print on B9180), one would have to make 739 prints at 11x17, or 138,193 square inches, to erase the $1145.84 gap in price between the iPF5000 and the B9180.
While I was originally keen to take advantage of some of the deals in the US on iPF5000 with roll holder, I think I'm leaning back to the B9180 as I don't see prints larger than 12x18 in my immediate future. Once the the 5D's successor allows me to move up from my 20D, that might change, but I also don't see myself making anywhere near that volume of prints in 5 the years that I could expect the unit to remain sufficiently current with regard to its gamut, tech, and reliability.
As for the 3800, with the iPF500 at $1400, I'm not sure that it is overly appealing.
Thoughts? Any of you old hands see any flaws in my analysis? Am I making a tragic error?