I've paid $400 for better condition ski's, and $400 for similar condition. So in general it's about right, assuming the MPEM is good, if its not, its a bad buy.
MPEM and Core motor are worth $320-$400 on their own, not to mention misc. So you realistically can't lose money on your investment even if you decided to give up and part it out, the worst that happens is you break even after fee's and a lot of wasted time.
The rest is up to you, your mechanical ability, and your willingness to invest time/effort.
By the time you look at rebuild, assorted issues like cables, battery,labor,carb rebuild, pump rebuild, and unknowns, you can very quickly be in the hole about $1800 on a $1600 ski, but it will be in good shape and probably under warranty at that point.
for a personal use purchase, and doing most of your own labor its a good investment but not a great one.
As a flip its a terrible investment unless you have enough parts laying around to Frankenstein an engine and you've done this before.
You probably wouldn't be asking if you had a pile of spare parts for a rebuild and this isn't your first rodeo. so I guess that goes w/o being said.
edit: kicker was posting as I was typing... we're pretty much on the same page, and he pointed out some assorted items that I missed in my haste (lines, mats, vinyl)