The reason this needs to be illegal is because jamming the signal is not specific to you. You block your signal but you probably will also be blocking it for anyone else in the vicinity. Plus the way these things work they can create interference for other types of signals as well. It isn't the blocking itself that's illegal, but the interference that you're causing.
OP didn't make an incorrect statement though. What they stated was an important part of the equation. I think a lot of people don't take that type of thing into account and they will read what this post says and assume that Pfizer should be charging $13, or maybe something pretty close like 15 or 20. Clearly 1400 is far far too high, 13 is too low. A reasonable price allows the manufacturer to be successful while not gouging consumers lies somewhere in between, but much much closer to the low end than the high. To me that's really what the person you are responding to is giving evidence for.
The reason this needs to be illegal is because jamming the signal is not specific to you. You block your signal but you probably will also be blocking it for anyone else in the vicinity. Plus the way these things work they can create interference for other types of signals as well. It isn't the blocking itself that's illegal, but the interference that you're causing.