Have you checked out these bikes personally?
Taken someone with you that has some experience?
Have you tested other bikes? If you deadset on one of these then R6k is an ok amount for the xcaliber, if all components in good condition, brakes working well.
Is it Tubeless, if not will cost you additional zar.
When last service, check if chain or cassette needs replacement soon.
If you can pay R5000 or R5500 then even better.
Seen similar spec bikes advertised for R6000 to R9000