The permanent with the ability needs to be on the battlefield to see you spend the mana
While Blue-Eyes has received tons of support, Red-Eyes has never really been a meta contender
"Dragon's Mirror" can also be included as a last resort, because if all else fails, it can be used to Summon "Five-Headed Dragon" or "First of the Dragons" for the finishing blow, because your opponent will have likely already exhausted most of their resources to deal with "Buster Blader, the Dragon Destroyer Swordsman", "Crystal Wing Synchro Dragon", and especially "Beelze of the Diabolic Dragons" and "Red-Eyes Flare Metal Dragon"
A safe bet is that a foil will be worth about 1.5 times its non-foil printing, which would put the average value of a foil mythic at $33.57 and the average value of a foil rare at $4.76
You may have noticed Ive mentioned creatures at lower mana values are somewhat undersized in The Brothers War , presumably to help slow the format down, but Red barely notices
In making up the primary list, I used a combination of criteria