DH wore his Fitbit to DLR this past March. One day he did 33,500 and another 31,700. He says he'd classify both of those as "light" days, since we have 3 young kids (including an infant) and took a lot of breaks (although we do go from morning until close).
We went to WDW last May and he logged over 30k each day there, but I was 27-28 weeks pregnant, so we also took it slow with a lot of breaks (including at least one table service adr a day). When everyone's in peak condition, he logs around 40k a day at WDW.
(The most he's ever logged was 43,850 in a single day. Daily avg is 20k. He's never logged less than 10k in a day, but he runs and always takes the stairs, etc.)