Not that I can remember my 1541 being rubbish.
"Not sure I'd use it as an example of something "magic"."
It had a 6502 CPU in it and when we run code on the 1541 and detached the cable and it did still run, it felt magic to me. Because it was forty years ago, I can't remember all the details but I think there was a copy program on two drives that run without the c64.
"and was almost as slow as a tape deck."
No it wasn't. When I loaded a game from tape, it was more: Start game, have lunch, play game (I really started loading before lunch quite often). With the disk drive it was: Load, Play. Most people used a fast loader on top of that (Can't remember but I do think I had an Action Replay, but it might that I had one for my A500).
"It cost more than the computer it came with"
That was the case with quite some floppy drives, e.g. the floppy drive to my Amstrad CPC back in the 80s costed as much as the computer too (and contrary to the 1541 I don't think it had a general purpose CPU in it).
[Update] It looks there is a fast loader from 2020 that can do 19k/sec just as an AppleII on a 1541, so it doesn't seem like it's the hardware https://www.c64-wiki.com/wiki/Transwarp