Case in point ... when I bought my Viper PST 6-24x50 FFP it was $750. I was totally disappointed in the optical quality past 12x. I should have spent another $750 as now I'm stuck with a scope that I've never and will never take to the range ... and now sells for $500 online.

I admit: optics are tough to splurge upon. I remember paying over $2,000 for my US Optics and thinking ... what am I doing? However, at teh time they were the best option for a LPVO. When I sold it several years later I lost about $150 in spite of being using (on a SCAR no less ... known for damaging optics ... ). My Aimpoints have lost around $100-150 of value but they're RDS. Think about the value of your TV or Computer vs what you paid. My ACOGs have probably lost $150-175 of value but they have tritium which dies over time.

All told, the value of higher end optics will decrease the moment you buy it .. but because it is higher end it won't be nearly worthless (like many lower priced options). I have a safe filled with Vortex (most still in the box) that I've had a hard time giving away (30% below what I paid ... new in box).

There will always be a market for cheap stuff. People are like that.
There will always be a market for top tier stuff.

The difference is the value the item offered the original owner and the value it retained when it came time to sell it.