Making lots of money on the collectable side is fine, but there comes with it a responsibility to reinvest in the core parts of the actual game the collectable is based on
That said, Id resist the temptation to stick some of the zero-drop artifact creatures like Ornithopter in
The ability also triggers if our opponent targets it with a spell, which makes it somewhat resilient to removal
(2024-06-07) Energy counters aren't mana
The reason that the card costs so much is that it is pretty much the number one most iconic creature from Magic during that time, with Serra Angel an easy choice for second place
Here are some good Nethroi targets that have low power but make tokens or have good effects when they enter: Biogenic Ooze Blade Splicer Master Splicer Maul Splicer Sensor Splicer Noosegraf Mob Chittering Witch Creakwood Liege Akroan Horse Pentavus Deep Forest Hermit Deranged Hermit Nut Collector Duplicant Geist-Honored Monk Ghave, Guru of Spores God-Eternal Oketra Hornet Queen Izoni, Thousand-Eyed Tendershoot Dryad Trostani Discordant Trostani's Summoner Most of the above cards create creature tokens, so you'll probably want the usual: Doubling Season, Anointed Procession, Parallel Lives if you include a lot of them