I bought my 10x40 on eBay of all places, paid not a lot for them because the rubber armour was falling off & they looked tatty. I sent them to Zeiss for a refurb & they came back fully serviced, cleaned up, new rubber armour, new rain guard, new strap, new objective covers (from a different model at my request but work a treat) & a nice new leather case. The cost was very reasonable, I don’t recall the exact figure but less than £200 from memory.
If you get them for £100, or even £200, send them away & get a price for service - if it’s too expensive sell them on (maybe part ex for a better pair at somewhere like London Canera Exchange for example?).