Pocket 380s are less common than the Pocket 9s, having been made in only 1986.
The ones I've seen go for around $350-$450. Some ask for more for theirs, but I seldom see them selling for much more.
As to the 'leather detonics case', we'd have to know more about it to know how much value this adds.

I picked up a Pocket 9 in it's original box w/ manual, a spare mag, and a 'Minuteman' custom leather pancake holster for $300, and that was a little under what they normally go for with all those extras.

Hope this helps!