Hi Butz - I ordered a K71 whilst I was in the Army in Germany in 1970. The kits had certainly been going for a few years before that although I'm not sure when they started. The price then was £80 (about $120) and they returned my cheque offering a NATO discount - for reasons I can't remember I never did get the kit!!
I finally got my hands on one in 1996 when there were still a few retailers offering them but could not find the K71 Monza so had the K73 Grand Sport instead (all the chassis are the same). At that time it was £236 ($357) so prices more or less trebled in 30 years or so.
Check out ebay and you'll see that prices vary a lot especially for started kits. This presumably is because of the possibility of missing parts and with nearly 2000 bits in the box its' not surprising.
Mine took me 15 months and I don't know how many hours to complete but in about 2002 I came across a RR Phantom on another auction site which I got for £90 and sold within two weeks on ebay for £345 - I just could not face doing another right then and the cash came in handy!
The one you have is so rare that I'd definitely keep it and have a go - take your time and they're are not that difficult. There are plenty of help forums for Pochers if you get stuck.
My K73 GS converted to a Zagato Spyder.
All the best and good luck with it.
Martin
http://www.freewebs.com/martsmodels/