Let me take a bit of a contrarian view.
I'll preface this to say, that I have no junked out cars or furniture, couches or the like in my front yard.
But I'm perfectly happy to take pretty worked-over demo stuff. As long as it doesn't have structural damage [edge compression, broken or blown edges, mashed sidewalls, or other damage that penetrates the core, etc] and it's cheap - I'm good with it.
I've invested in most of the tools I'd need for these kinds of jobs. PTex work is really pretty easy with a fairly cheap iron and sticks of ptex. I have base flattening and structuring tools too.
So, if you're willing to learn - get your hands dirty, risk screwing up a ski - then buying a ski like in the parent post can work just fine. I'm pretty handy - and do/have done a fair bit of pretty advanced wood-working, have epoxies, metal scrapers and experience. That all inspires confidence. Having done some more elaborate wood-working projects, I'm reasonably certain where my skills and deficits are too.
I might have $150-200 in tools, but they have earned their keep, and now I have those tools to handle anything I want to do myself - even if I never buy another "used" ski that needs repair again..
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A few years ago I picked up a Mantra that had a couple of edge-compressions and related damage. I paid a pretty minimal sum for them, and could have simply stripped the bindings and sold them on and lost nothing. So, I felt reasonable [low risk] in doing my own epoxy work, straightening the edges, and getting all the compression out that I could.
I eventually sold them to a friend - disclosing their history, after I skied them myself for a few days. I found a few hidden rock-sharks, myself, on some early season skiing - which I also repaired. I made money on them - though not a lot if you consider what my time is worth. But it was good experience, fairly fun - and I have a less anxious time around rocks and "early season" conditions. [All season conditions in the PNW this year.]
Interestingly enough - I suspect this ski was a defect from the factory. My guess is that it was glue starved. [They didn't put enough epoxy in the ski when it was pressed.] The result was that water was able to partially penetrate the ski in a few places. I think that corroded / rusted the edges, internally. This finally resulted in pull-out in those locations when the ski was semi-abused. [Accidents do happen - so abuse is probably too strong a word.] The result of the impact was more dramatic because of the water penetration. [This is, obviously, my wild guess - it could be completely wrong - but that's what makes sense to me.] The reason I mention this - if you decide to take on a project - remember it may be a "project" from causes that are more systemic than you might consider. It might not just be that someone blew the edges - the edges might have blown because there are bigger problems with the ski.
And one of the other up-sides to being willing to play ski-fix-it is; I pick up a fair number of skis - I'll pass them on to friends at minimal mark-up. But I also get a chance to ski them and get wider exposure to what's available. And I make money doing it.
That's a lot better and cheaper than a "demo" day. I can keep a ski a day, a week, a year or several years - with the assurance I am pretty unlikely to lose any money on the deal. And I have a lot of fun sharing skis with friends and others I meet - they like it a lot too. If you're in my neck of the woods, [Mt Hood Meadows] I'm probably glad to let you try whatever I've got that I'm not skiing myself, that day.
Good times for everyone.