I took a look in my old magazines, and in 1984 you could get an 8086 based Advance-86 (but not PC compatible, you had to pay extra for that) for £399. Obviously it wasn't a match for the Amiga, and probably not the Atari ST either, given the 4.77MHz 8086. But neither of these was out then.
Amstrad came out with the PC-1512 in 1986, for £499. This was PC compatible, came with 512KB RAM, and an 8MHz 8086 - and a monitor. This could do 16 colours at 640x200, and it also came with GEM as well as DOS - so more than a match for the Atari ST in many ways. In 1986 this computer was a bargain, at least in the UK.
But as soon as you started looking into 286s, 386s and 486s later on, the prices just rocketed - but the PC started relying on CPU power instead of graphical ability for games, and that brings us to Wolf3D, Doom and Quake, and the rest is history.