Seems like a fair offer to me, doesn't hurt to say no after all...

Bender is quite right about rusty fork tubes. Absolutely no sources I am aware of for tubes for the 125/175 series, other than Frank's Forks. A few years ago, when I was rebuilding a '68 DT1 there was an aftermarket source that I do not recall at the moment (perhaps someone else may recall??)

The early AT1 fork tubes I got from Frank's were $400 + shipping. For those you must send him your old ones as the bushing and clip at the bottom must be removed and re-installed on the new tubes (part of the job).

Steve.
Dachi / DC Plastics used to sell reproduction 34mm tubes for 68 dt1 but 2-3 years ago no longer carries those tubes as supplier quit manufacturing them.    
At that time other forum members commented Allen Industrial Hard Chroming in Banning, CA did a good job with quick turnaround at a very fair price.  
Steve

Have you checked out the supply of decent parts lately ? Nothing of real consequence at a good price anymore.
knock off fuel taps, chains and sprockets mostly on ebay uk. If i lived in the US id be like rollin rollin rollin keep them DTs comin , raw hide ! Yhaa .