Like most things, quality and demand determine cost. The best poker players in the world often cost $500+ per hour for a 1-on-1 coaching session. Mid-stakes poker coaches are typically in the $50-$200/hr range. Low-stakes poker coaches come in below $50/hr.
Because these prices are often a major hurdle, there are many poker training sites that charge a monthly subscription for access to videos. This is a lower price-entry for the consumer. This does not fix the high cost of 1-1 coaching however.
Poker stables, like Pocarr, can provide free 1-1 sessions that are effectively paid for out of future winnings, via a staking deal. Pocarr provides the capital to play and coaching resources, and takes a percentage of profits. This model is beneficial to the player, the coach, and the staker. The player gets coaching with no out-of-pocket cost, the coach gets more coaching hours, and the staker gets to financially stake a quality player who cares about improving their poker game.