Define 'decent'.

Since ~ 1995 a decent PC (runs everything, not a mind blowing rig) were always around $2000 with monitor, with a sharp decline to $1000 around late '00 and a slight increase since then but there is nothing a $200 GPU with a decent CPU and enough amount of RAM can't what a rig $4000+ can't do, only slower.

I still remember what I paid for a PC in 1997.... $3500 for a dell with 128MB of ram, 400 MHz Pentium II, 10MB HD, zip drive, 21 inch monitor... My wife's company paid for half of it.. otherwise would have bough a cheaper one... 2 years later you could buy all that for less than half with a 1GHZ P III