according to recent price lists, my coins have
almost all gone up in value and are now worth about $6k as opposed to
the $4k I paid for them a year and a half ago.

You are making an apples to oranges comparison. The prices you paid on ebaY do
not compare to the retail prices on the PCGS boards.

Looks at recent sell prices on ebaY for an apples to apples comparison. That
will give you a more honest picture of the change +/- in value.

Regards,
Tom