Yeah I read your daughter restored one of the DX's, impressive!
When I bought mine it was a non-runner, all the problem turned out to be was the big rubber seal that seperates both halfs of the crank/crank case.
Yeah i'm surprised at how much they're going for now!
Don't think I would of got those values for my one though as it was far from a restoration, more of a project/fighter bike, not many standard bits left on it etc.
I only payed £100 for it and mainly bought it as a first bike and to learn how everything works etc as I was learning to be a mechanic at the time, albeit a HGV mechanic lol.
The money I lost in binning it didn't really bother me, it was just the man-hours put into it..
Anyway, at risk of de-railing your thread i'll be quiet now lol.
P.s My SV is a silver 2003 one too! Your Ex looks a natural on the track