Counting the cost of "Are slots worth it?" starts with the stake per spin. Penny slots and progressive jackpots sit at opposite ends of the same machines. One promises a small stake, the other a huge prize, and both are less simple than they look. What a penny slot really costs per spin, how a jackpot meter grows and what the odds of hitting it are decide whether either is worth playing, and neither rewards a strategy the way their fans expect.
Progressive jackpots work by taking a small share of every stake and adding it to a prize that keeps growing until someone wins it. The jackpot meter on the screen shows that running total, and on networked games it rises with stakes from many casinos at once. A mystery progressive jackpot is paid at a random moment before the meter reaches a hidden limit rather than on a symbol combination, so any spin may trigger it.
Penny slot payout rates are usually lower than those of higher stake machines, because operators set a lower return to player where stakes are small. Penny slots still exist in large numbers, though they look like any other video slot, with bright themes, many lines and bonus features rather than the single coin slot of old. Whether they are worth it depends on treating them as entertainment; how to win on penny slots has no answer beyond luck and a fixed budget.
Often they do: machines with low stakes tend to carry lower payout rates than those with higher stakes. The rate is in the game's help screen.
A small share of every stake on the linked machines feeds the meter until someone wins it, then it resets to a seed amount.
Set a budget before the session and treat the jackpot as a rare extra, never as the reason to keep playing.
Each active line takes a coin and each bet level multiplies it, so a machine with many lines can cost many coins per spin.
In entertainment, not in income: every slot returns less than it takes over time, by the share its RTP leaves out. A budget fixed in advance is the price of the time played.