In 2019, a rare Black Lotus card from Magic: The Gathering went for more than $166,000 at auction more than doubling the cards value.
When it comes to three-mana ramp cards, its often better to just play more interaction and slow the game down instead of trying to ramp
Summon: Primal Odin Six mana is a totally fair rate to pay for a big Nekrataal in Limited, and Summon: Primal Odin also has two other interesting chapters
Sword of Truth and Justice is another one that is pretty good with Venser as the commander since it gives him (conditional) evasion, proliferates, and adds +1/+1 counters to grow your creatures which the deck has very few ways of doing, but I absolutely would not spend $30+ for the card, it's not that good
We have seen this with Spell Pierce, where players go and spend three or four mana on a card for you to only spend one and instantly swing the game
One one hand, it's only played in one somewhat untested Modern deck