I've not seen a .44 mag 788 in a long time. I do frequently see .308 and .243 versions and they are not usually any less than $375 and typically in the $425 to $500 range, depending on condition. My father still has a .222 package version with a 4X scope that he bought new in the early '70's. It is still in new condition. I believe he paid $124 back then.
If you really like the gun and are not in need of the cash, I would keep it. As you say, they are hard to come by. Should financial issues occur, you could always sell it for decent money.
EVOC ONE