I am liking one I bought +3 years ago. But it’s a 18’.  Bit small.   Well today looked at 21’ maybe 22’ ÎF I measured right. Not bad. Not near as good as my 18’. Especially disc blades.  I think original supposed to be 18”  or 20” they were barely 14” it had shank protectors but few left, many new towers, the shovels Need replacement soon, drag has few bends, but useable. 
  I forgot to count but I figure +31 disc blades. $40 to $76 options *if 20” original size*  so possibly $2300. ÎF they are supposed to be 18” need to check model ##. Then $25 to $55 I think so $1700.   But of course bearings. I might recycle 50% of bearings at most.  *the closest to nut* $50 to +$70 each. So 6 I think? $420.  But the labor! Might as well replace every bearing. $850
  So 3’ figure +$3000 plus purchase price, labor?  Every 6 rounds I get one *free* round.  Plus shank tips rather worn. So that expense in Á year.  For 16% wider swath?

  I figured an insult to offer what at time I figured it’s worth to me. Now I am thinking even less.   Maybe set front a bit deep, max set on discs they might cut stalks?  Put new rear shovels first. Then replace front with used off rear? Might get few years.   
   My thought tonight.  Wait till mid April.  If he still has it text him my offer that’s 1/3 his asking price.  He gets mad?  Oh well. I’m thinking as possibly useable.  *he said they no longer tried to use disc blades*   
  Maybe with time I can find blades cheaper.  *I did find correct bore, overall diameter, thickness, but they looked beveled 20” $25 each. And Á notched version $20 each.   Never seen notched on one?  Waves yes.   Nice thing small sections about +5’ long. Only two points so I think easier than most disc units to replace.    
  If nothing else instant spare parts.  The nuts on disc shafts were worn A lot.   I worry I might not be able to use impact.  Monkey wrench, heat every one.  Plus damaged thread ends.  Putting nut on after might be fun.. yep 1/3 his asking price after few weeks ÎF it’s still listed.