Most older booster boxes are expensive for a number of reasons, but mainly because of scarcity

Here are the banned cards for this format: Ancestral Recall Balance Biorhythm Black Lotus Braids, Cabal Minion Chaos Orb Coalition Victory Channel Emrakul, the Aeons Torn Erayo, Soratami Ascendant Falling Star Fastbond Flash Gifts Ungiven Golos, Tireless Pilgrim Griselbrand Hullbreacher Iona, Shield of Emeria Karakas Leovold, Emissary of Trest Library of Alexandria Limited Resources Lutri, the Spellchaser Mox Emerald Mox Jet Mox Pearl Mox Ruby Mox Sapphire Panoptic Mirror Paradox Engine Primeval Titan Prophet of Kruphix Recurring Nightmare Rofellos, Llanowar Emissary Shahrazad Sundering Titan Sway of the Stars Sylvan Primordial Time Vault Time Walk Tinker Tolarian Academy Trade Secrets Upheaval Yawgmoth's Bargain MTG Standard banlist Here are all the banned cards for MTG Standard: The Meathook Massacre Fable of the Mirror-Breaker Invoke Despair Reckoner Bankbuster MTG Modern banlist Modern covers Magic: The Gathering cards from the eighth edition to today: Ancient Den Arcum's Astrolabe Birthing Pod Blazing Shoal Bridge From Below Chrome Mox Cloudpost Dark Depths Deathrite Shaman Dig Through Time Dread Return Eye of Ugin Faithless Looting Field of the Dead Fury Gitaxian Probe Glimpse of Nature Golgari Grave-Troll Great Furnace Green Sun's Zenith Hogaak, Arisen Necropolis Hypergenesis Krark-Clan Ironworks Lurrus of the Dream-Den Mental Misstep Mox Opal Mycosynth Lattice Mystic Sanctuary Oko, Thief of Crowns Once Upon a Time Ponder Punishing Fire Rite of Flame Seat of the Synod Second Sunrise Seething Song Sensei's Divining Top Simian Spirit Guide Skullclamp Splinter Twin Summer Bloom Tibalt's Trickery Treasure Cruise Tree of Tales Umezawa's Jitte Up the Beanstalk Uro, Titan of Nature's Wrath Vault of Whispers Violent Outburst Yorion, Sky Nomad MTG Vintage banlist The vintage format lets you use any card from Magic: The Gathering's history - apart from banned cards

What is the rarity of this Mewtwo ex card
2/2 creatures are really easy to deal with and they dont do so well in combat, something which has gotten more prevalent in recent sets as 2/2s for 3 have become majorly outclassed by even the vanilla creatures in modern sets
It should also do some heavy lifting in Vampire aggro decks as an evasive beater that can stabilize your life total
Getting all Commander 2019 or 2020 decks would be cheaper than buying one of the Commander 2017 decks, so there is that