i know that there are other ways but most of those ways are just spending real money and there is also only a 1,5% chance to get the legendary you want through the shiny legend crate and most people only want 1 of them so thats why i think it should be sold you could also make it so you only buy...
The red chain is an item you need to summon Dialga Palkia or Giritina and its really hard to optain i think it should be possible to buy it for 100K in a shop or something i know legendarys are supposed to be hard to get but to make the red chain you need to catch the lake guardians which is 3...