Value of Sennheiser Orpheus headphone system?

Folks: I have the opportunity to purchase a Sennheiser Orpheus headphone system at what I consider a reasonable price. Frankly, I don't think I'd buy it to keep, but to sell onward, hopefully at some profit (so I can buy other stuff I need more). The question is, however, given the limited production of these units and hence general lack of "consensus" pricing for used units, what does anyone imagine the "going rate" would be for an Orpheus system in excellent condition? I know what they sold for new -- I doubt that the value has increased, but how far do you think it has fallen off the original $15000 price? Thanks for any thoughts you have.