AMD's 386 and 486 clones were always cheaper than Intel's, and they always at least matched the clock-for-clock performance of Intel's direct counterparts.
But back in those days, Intel always had a faster CPU on the market somewhere. Eg: when AMD's 386s were at 40Mhz (vs Intel's 33), Intel had 486s. When AMD's first 486s came out, Intel had 486DX2s, when AMD's clock-multiplied 486s appeared, Intel had the Pentium. Etc.
AMD having the fastest chip on the market - which they only did for about 50% of the last 5 years, despite their general dominance - is very much a blip on the radar.
AMD have, however, often ruled the price/performance ratio at the lower, end, I'll grant - but in that market they have been plagued by buggy chipsets and cheap, low-quality motherboards. VIA has done more to hurt AMD's acceptance in the mainstream than Intel could ever have hoped to do.