Thanks for the tips! Had thought about the downside to shipping charges. But I hadn't thought about a defective cartridge, as I have never encountered one before with my Dell Printer. All I have local is Circuit City & Best Buy, which charge the same as or
more than Canon direct on-line. Unfortunately, the nearest Fry's is in Austin an hour away.

But we drive down there 1-2 times a month, so looks like I'm going to be finding where the Fry's is in Austin. Thanks for your help, Steve.
For anyone interested interested in my search findings, Abacus24-7.com is
two dollars less for the PG-50 black hi-yield;
four dollars less on the CL-51 color hi-yield.

And they are
"Genuine" Canon cartridges, not what is called Compatible, Refurbed, Remanufactured or OEM. Bizrate.com gives this company a good rating.