Stuff like this tends to follow the price of scrap iron, and scrap iron is way up the past 2 years.
Was at an auction last spring, and a old worthless row crop cultivator brought $400. Scrapper bought it. They used to go $50 for scrap on a good day.
Do you have clay or sandy soils? Field cultivator is better in clay and wet ground, disk is fine in sand. For what my opinion is worth.