Does raising speaker cables off the floor really make a big difference?

Yes.  Carpet static electricity is a real issue, especially where I live. Also bought a "grounding pad" that I touch before I touch any of my gear. And I went cheap and used CD plastic cases. Total cost under $20.  This raised some 70' of speaker cable off the carpet.  Audible drop in system noise floor.  Less noise, more music.  Pretty simple concept.  Whether you can hear or not depends on the overall transparency of your system.

Static electricity can be caused by friction, electrostatic induction or electrostatic conduction. I am no physicist but it appears the static phenomena between the wire and the carpet fibers is caused by either induction or conduction.

Charging by conduction involves the contact of a charged object to a neutral object. In contrast to induction, where the charged object is brought near but never contacted to the object being charged, conduction charging involves making the physical connection of the charged object to the neutral object.

I’ll leave it to others to determine which is the cause. FWIW, static is more likely to exist in a drier climate versus one that has higher humidity. That may be the reason some experience no sonic impact from elevating the speaker wire from the carpet.

If you some cd’s, you can try this simple experiment (raise wires off the floor with the case) for $0.00 and a couple of minutes of your time and determine if you can hear the difference or not.

I have no clue as to why folks think "raising wire off the floor" is a "cash cow tweak". There are numerous ways to do this and spend a pittance of money. Cups, CD cases, etc. Seems to me these individuals have little interest in experimenting with their systems to improve the overall sound. One must ask why they are commenting on something when they have no practical experience to back up their claim.

Because he is obviously too lazy or too jaded or just trolling or just doesn’t care about the sound quality of his system and then has the arrogance to criticize a tweak he hasn’t even tried even though it costs almost nothing (or $0.00) and takes a matter of minutes to determine its efficacy. I love it when people "judge" something without any basis for that judgement. Ultimate hypocrisy. As Forest Gump said, stupid is as stupid does.