I can't comment on your other prices but I will say one thing:

You do NOT want to buy a new 12 R 30 (30ft) front fold toolbar that is priced at "10-15k" as you thought. The materials cost to manufacture a decent, durable bar of this type will cost at least that.

You may be able to buy a worn out 12R30 planter for that then remove the row units and put the new Case 1200 units, air box, Rawson drive, etc on it but good luck on the pivots, cylinders, markers, tires, axles, bearings, etc.

Or go with a vertical fold/lift assist wheel design which is generally less expensive to build. Probably the best value in a quality 3-point 30 ft bar I have seen is a Moore-Built out of Nebraska but by the time you get done specing it out it will still probably be more than "10-15k". A front fold design is inherently much more expensive to build. Best of luck.

Jim at Dawn