Least expensive discrete resistor ladder NOS DAC?

Check out Linear Tube Audio. They sell MHDT models and another brand of interest that has been mentioned on this forum, however i forget the name. All are R2R NOS DACs.

Check out the multibit DACs from Schiit.  Not sure if they are discrete resistor or not (although I assume they are).  There are three of them under $2,000 new.

If your talking about the BB 1704 U - K / J these days only the J version is available. They go for up to $200 per IC for a genuine one - lots of fakes out there. So for a complete DAC your budget will be hard to meet. A bargain in a R2R discrete DAC is the Denafrips DAC’s starting at $750 or so - the Ares their entry level one is an exceedingly good value. It has some interface challenges - impossible to read gray screen on black and 1mm LED indicators - other than that a great sounding unit.

Good Listening 

Peter