Opps, just reread your post, you mentioned M44. The costs should be very similair
Yes $1,200 is very expensive. Typically $300-450 is what it will cost.
You will want to rebuild any used M42. They have several flaws which can lead to engine failure in higher mileage engines.
Typical rebuild costs are about $2,500-$3500 for a complete rebuild that also addresses and corrects several of the original problems. Thats my price anyways.
Factory rebuilt engine is about $4,500 and a full blown built M42 from Metric Mechanic can reach upwards of $8,000.