Such things are limited in their effectiveness. When you open the wine it comes into contact with air and begins to change. Even with careful handling, vacuum stoppers, inert gas covers like Private Preserve, the bottle will be spoiled in just a few days.
With Coravin the wine is never opened. Never meets air. Stays unchanged for as long as you like. You can pour yourself one glass of a costly wine, then wait a year to pour the next. No issues.
Yes, it's expensive both to buy & use. It only makes sense if you're handling higher-end wines. My brother-in-law was working for a distributor and had limited access to samples. Using coravin he could keep a sample of a fine wine for a month or more, confident that it'd be perfect each time he poured it for a restaurant owner.