...steer clear of used R2R DACs, since their reliance on high precision resistors causes them to sound best when new, and degrade fairly quickly...
I think your sales person is trying to sell you a new DAC.
My R2R DAC is a Theta ProBasic III that is more than 20 years old. I love the thing as it does it does not have that treble edge that one hears in so many "modern day" DACs.
Listed new for $2,700 and I bought used about three years ago for $600.
Thanks for listening,
Dsper