Maybe a typo, but 380SE's were '84 and '85. If it's a 1981, it should be a 380SEL.
The price is quite steep. Retail blue book looks to be in the low $6k's...
I bought a 1983 380SEL with 85k miles on it for $6600 (Southern California). Was in beautiful shape - garaged, practically perfect interior, had dual-row timing chain conversion done on it already.
But, if it's in good shape and checks out at a mechanic, work on bringing the price down and you'll wind up with a wonderful car! Smooth and quiet - makes for a fantastic freeway cruiser.