The machine on that price list at $1,565 had no disk drive at all. Sixteen kilobytes, a keyboard, a graphics card, and a port for a cassette recorder. With no disk in the machine you came up in BASIC out of ROM, and that was your computer for the evening. A monitor and a single floppy took it to just over three thousand.
The hardware was nothing special. The 8088 was 16-bit inside and talked to everything else eight bits at a time, which was IBM taking cost out of a chip that already existed. What mattered was that the bus and the memory map were published from the start, so anybody could build a card for it. The BIOS was the one part they kept, and the clone makers had to reverse engineer that the careful way.
Which is why I give the credit to the paperwork rather than the machine. There were better computers in 1981, and most of the ones that kept their insides to themselves are trivia now.