My first IBM compatible was a prebuilt(small shop) 486DX50, probably around 1992, but I'm not sure. The only chip faster at the time was the DX66, if anyone feels like researching release dates.  I payed $1,700 for it, but I don't know if that was a good deal or not. I got it at a computer show, and back then those things were major events. Super crazy inside, and if you didn't come prepared(I didn't :^/), it could be overwhelming.