While Lifeblood Hydra’s price spiked to $18.99 on 7/18/19, that wasn’t a real price - just what it was being listed for after being bought out all over TCGPlayer. Keep this in mind when you see price spikes and check trusted retailers for their current prices. Those prices are typically going to be far more reasonable, unless those vendors are also buying at an extremely high rate in order to keep that card in stock.
However, Lifeblood Hydra is a good card and $5 for a card that can gain you significant amounts of life and card draw when it dies is not a bad deal. He currently only has two printings, too, one of which is Commander Anthology. Since Gargos has an ability to make Hydras cost fewer 4 generic mana to cast, when Gargos is on the board, you are paying only 3 Green mana to get an X=4 Lifeblood Hydra with four +1/+1 counters.
Getting 4 life and 4 cards when Lifeblood Hydra dies for an investment of only three mana is absolutely nuts. Add to that Lifeblood Hydra has trample and you have a very solid creature. This guy was $2 forever and just needed a permanent home. He found it.