For Frank Robinson, it's $99 for a "regular" item, which they define as "Any size flat item, baseball, cap, or mini helmets." All other items are classified as "premium," and it's $229 for an autograph on those.
Regarding steve B's comment about buying just the inscription without an autograph: it doesn't say anything on
Robinson's page, and presumably the same is true on the other players' pages, but at the top of the
autograph ticket page it says "Note: Inscriptions must be obtained at the same time as the autograph, and cannot be added to previously signed items.
If you plan to purchase an inscription ticket, you must purchase an autograph ticket. You cannot enter the autograph line without an autograph ticket." (Bold added.)