Eberron dragonmark magic items

[Gwyllgi]

How do these work canon, as far as I've read a lot are just made and require a dragon marked user to activate but I can't find specifics. Can persay any marked user of the proper fam use even the strongest dragonmark wondrous objects or would they persay by canon require a siberys wielder? In addition why don't the creation costs of the item require crystals from what I've read.

[Falontani]

The Crystals are a fluff requirement. The dm can and should require certain powerful magical items, or magic items linked to Dragonmarks require more and more refined Dragonshards.

With that said from a mechanical point of view, requiring someone to have a Dragonmark to activate an item should count as both a race and feat requirement, meaning with custom magic item rules, should get both a 30%, and a 10% discount on item creation cost, however I'd only allow you to do it to items that are thematic for the Dragonmark.

This also lets a wide number of people be able to use this item that otherwise by RAW would require a skill investment, race requirement, and perhaps alignment requirement to use.