I think that, if we define a personal computer as a machine that is designed for a single interactive user, the LGP-30 would be a good candidate. It was not, however, a home computer.

For me, a personal computer needs more than switches and LEDs as its UI. With a serial port, a terminal, and a monitor program in ROM, the Altair would qualify.

The Wang 2200 looks most like we'd expect a personal computer to look like, but the price range was not home-friendly (~$50k today).

https://en.m.wikipedia.org/wiki/Datapoint_2200

The 6502 line came out Motorola's failure to "indulge" their employees in a low-cost 6800, thus unintentionally fathering MOS Technologies.

https://en.m.wikipedia.org/wiki/MOS_Technology_6502

The 6502 was extremely inexpensive. The first implementation was the KIM-1, so this is the first on that side.

https://en.m.wikipedia.org/wiki/KIM-1

Apple had the II in the late 70s, and before that was the Altair.

The Altair, in 1975, was the first commercially successful personal microcomputer.

The company sold itself to Pertec for what was a very good amount of money back then.

In HN terms, it was a successful unicorn bro exit.

So adapting the Intel 8008 emulator/assembler to the Intel 8080 was easy, compared to starting from scratch (and wondering if it was even possible that writing an 8080 cross-assembler/emulator would work).

Monte Davidoff has written a math package for PDP-8 so he was hired to write the math package for their BASIC for $400 + more in consulting fees.

Both the Intel 8080 and Motorola 6800 were introduced at $360 - many references to the IBM 360 mainframe computers as the inspiration for this price.

Ed Roberts was able to negotiate thousand Intel 8080 CPUs at $75 (vs $360 list price). A retro computing website mentions that these CPUs were less than perfect somehow, though still functional.

Back to Paul Allen's book, the MITS Altair was originally introduced with a whole 256 bytes of memory. To increase profits, the included memory card was ditched and you had to buy a memory card ($176 or 1K or $264 for 4K - amazon.com sells DDR5 64GB for US$150-$200 today)

    When Intel and Texas Instruments ran short of memory chips, Ed turned to an off-brand called Signetics, whose chips were hopelessly flaky. I started getting calls, less friendly this time, from people who’d invested in 4K of memory and still couldn’t load BASIC. I’d see Bill Yates tearing his hair out in the engineering department over defective Signetics cards. As David Bunnell and Eddie Currie later acknowledged in PC Magazine, “. . . the probability of getting a 4K memory board to work when assembled from [an Altair] kit was remote. And the likelihood that it would continue to work would easily have been rated zero.”

a couple of decades later (i hadn't listened, and had been working for high-tech Silly Valley for quite a while) he apologized :-)

https://en.wikipedia.org/wiki/Programma_101

(It all depends on the definition or what a personal computer is)