Back in the 80's they retailed for about 2,000dm and the piano finish like mine for 2,500dm which converts roughly to Euros. So not a cheap model.
They are very rare in UK but are seen reasonably often in Germany (home market), the United States and strangely enough, old Iron Curtain countries.
I got a link to mine through hifishark.com
A Black or Satin wood finish go for £400/500, piano finish £600/700 in good condition. I've seen a couple of slightly tatty but fully functioning black pairs go for 285 and 300 Euro.
Like most large speakers (21kg each) they tend to be collection only and being the age they are, have no shipping cartons. I had to pay for collection in Germany, the company (MBE) arrived by car, wrapped the speakers in blankets, put them in the boot and took them back to their depot for packing. Fedex then brought them to my address in the UK. This process, cost nearly as much as the speakers, but the examples I have are mint and well worth the money in my view.
They are cheaper than NS-1000m but for domestic listening, I think they are better. Not as forward at the top end, so more amp tolerant and that deep bass which is lacking in the Yams.