Hey L-L,
The MP-780 is no longer an option unless there is one sitting on a local shelf near him. There hasn't been a one on eBay in a good while. So the OP has really two choices. An MP-780 is almost worth any price as it will save that much in consumables costs - so it is worth checking every big box store in a 100 mi radius to ferret one out (at least to the east there isn't much land within 100 mi... 😉 . But living in or near Beantown, he is probably SOL as those thrifty students have grabbed them up long ago.
1- Excellent printing but relatively high consumables cost - Canon MP-? current model that uses the 5 and 8 series separate ink tanks - see other threads here on Canon ink tanks and others looking for AIOs for details. I'm tired of rewriting them. Some of last year's models may have lots of good deals as new ones are coming. Ink costs can be made reasonable by refilling your tanks. Some clone tanks for the 8 are here now others are supposed to be coming. See related threads for details.
2- Very nice scanning, networking, fair printing quality and not very fast (unless they have some new firmware to speed things up): Brother MFC-640 ($150. AR at Staples this week). The Brothers are the only current AIOs still using passive, separate ink tanks with clones available and refillable. So they have relatively low consumables costs and low hassle as you don't HAVE TO refill unless you want. I think all Brothers in the new series have internal modems, so faxing can be done with PC disconnected. All have at least 10/100 LAN connector and some (e.g. the 640) have wireless networking built in too (a card is available for others).
I would also suggest getting a Canon iP4200 (or the new replacement, iP4300, that's almost here). The shelves have almost been cleared of the 4200. About all I could find at well-known resellers were refurbs from Outpost.com a while ago when I looked. Same ink issues as Canon MP series but HELP is supposed to be "on the way". See other threads for details. And a separate scanner - tons of Epsons on eBay for cheap. And a fax-modem in your PC for faxing. And a copy of Smith-Micro's HotFax Message Center 6 (search in Hot Deals section, on HotFax, for thread on 40% off thru EOM) to handle Fax software needs. Don't buy AIOs unless forced. You can build or buy a stack rack to alleviate crowded work-surface problems. One part breaks and all has to go to shop or be replaced. You'll be much better off in the long run.
The one drawback of separates is that you must have the PC on to do copies and faxing. For home use, that shouldn't be an issue.
.bh.