Jim:
I hate to tell you but we all have that problem. I am in Sn3 and finding an engine under 800 is a challange. Somewhere along the line we lost all reason and added more to the engines than are really necessary, like front tube sheets and opening smoke box doors. If you watch as the other fellows have said you can find buys on some pretty good stuff although not always without some work afterwards. West side made a whole series of K-27's back in the early days and sometimes you can find someone that is getting rid of some equipment. One place few people check is with their local MNRA group. Frequently they have a member who has died or is getting out for one reason or another and they usually sell for less since ther is no dealer markup involved. Check it our it would be worth the cost of a membership if you hit a mine.
Good hunting. If you find one in Sn3 (PFM OK) for less than $600.00 let me3 know.
Frank