I often see people asking whether they can still purchase the Earthshaker Arcana, or the Windranger one or Wraith King etc but the answer is always "no" because they were tied to a Battlepass or were only available for a limited amount of time. Valve could make a lot of money re-offering these Arcanas for sale etc but they choose not to, they were only available for a limited time and they stick by that.
On the one hand I think that is a really good thing because the people that have them don't feel like they wasted their money/time getting them in the first place and they feel exclusive but on the other hand you could think of it as Valve creating a 'demand' around these exclusive sets and therefore get more money from people leveling up Battlepasses etc.
Should Valve re-market old Arcanas for sale to everyone or keep them exclusive?
Source: https://www.reddit.com/r/DotA2/comments/qr3qd3/if_valve_is_all_about_the_money_then_how_come/