The same argument was raised back in the 70's when it came to high-end audio cable.
$20 a foot Monster cable..or a cord from a lamp..no difference that the human ear could handle.
Depends on the ears! Some people say it makes no difference, other like me say it can. And since you're from C.R. all you had to do was go down 1st. Ave to Zuber's Sound Around back in the 70's where you could hear a big pair of Ohm speakers hooked up with regular 18 ga. zip cord and another pair with the early Monster speaker cable. You had to be nearly deaf to NOT hear a difference.
I've done my own tests with a few different sets of cables and between a certain two (Monster Interlink 400's and some cheap Kimber Kable PBJ's) I could pick it right every single time.
A few years ago somebody set up an ABX comparison test to try to prove an audiophile wrong. The guy (audiophile) did so well that not only could he tell the cables apart with 100% accuracy, he could even tell when the relays iin the comparator were being inserted into the signal chain! You don't do that good by guessing, that's great hearing.
As far as
"After all, it's digital, either the signal gets there or it doesn't." I can say that's not necessarily true. I've seen cheap cables have problems at a certain distance (both HDMI and DVI) while better quality cables had no issues at that distance and even many feet further.
Since I do telecommunications for a living and handle CAT 5 and CAT 6 nearly every day I know there's a lot more to it than
"either the signal gets there or it doesn't." There's signal attenuation, impedance matching problems, delay skew, propagation delay, NEXT (near-end crosstalk), FEXT (far-end crosstalk), PSNEXT (power-sum near-end crosstalk), ELFEXT (equal level far-end crosstalk), TDR (time-domain reflectivity), Return Loss, etc. All that just for using twisted pairs in a tight group that does a relatively good job of cancelling out noise, EMI, RFI, etc at 100 mhz (CAT 5) and 250 mhz (CAT 6) so you have your internet. Now go even higher in bandwidth to what you're dealing with Category 2 HDMI (340 mhz) and all of those things that I mentioned about CAT 5 & 6 become even more critical. So if you were truly a techie you'd know there's a heck of a lot more to it than just "After all, it's digital, either the signal gets there or it doesn't."