You must be looking at dates far out. I only see return airfares on AC for 5K plus. I'm thinking these fares were most likely bought on short or shorter notice for CC fraud to work. Since pax only flow AC, comparing prices from different airlines is like comparing apples to oranges.
Still seeing RT J at around the US$2000 range for dates in June-Aug and $1800s Sept-Nov (although the direct nonstop on CA is $2700 in the summer and back to $2200 in the fall). Perhaps you can get someone to help you with using a search engine like ITA Matrix. And, by the way, JL, CZ, HU, and MU have excellent hard products, and I'm speaking from experience.