I have found this Dell ad in an old issue of Byte magazine from Sept. 1990.

Dell i486 25/33MHz (click to read)

The prices range from $6,399 to $10,799 which corresponds to about $10k to $18k in 2008 dollars. The great features available for that price in 1990 were 4MB of RAM, 800×600 graphic card, 80MB to 650MB hard disk, and a 5.25″ 1.2MB floppy drive.