I haven't been looking lately, but I've seen several decent-looking/sounding YZ125Ds sell (or fail to sell!) for ~$1100 in the last 12~18 months. I sold mine for that, but it had a dodgy gearbox and 250D suspension (one step back, another step foward).
Can't say that I recall seeing a really good one change hands recently, but the good race RMs and CRs I've seen have still been under $2000.
Funnily enough, the YZ125C/X seem to be worth more than the 125D, despite being an inferior bike.
The 250s are always dearer than the 125s, esp in this era - as a rule of thumb, add about 50% to the 125 price for a similar 250.