Any one knows about Bimmers?

I just recently purchased a 1992 BMW 325is,it belonged to my girlfriends mom.She owned it for the past 15 years.The vehicle has 77,400 miles and had been kept inside the garage for most of the time.I bought it for $4,000.The vehicle has sunroof,leather seats,a cd changer in the trunk and has been well kept.my question is:is this the right price to pay for a 1992 BMW with this low mileage?