If you raise the minimum wage to $100 per hour, there will be no customers for the product or service affected.
At $15 per hour, some of the customers will disappear. Every job will disappear which doesn't generate sufficient revenue to justify the wages. Every wage increase changes the criteria for justifying the existence of that job.
In some cases, the customers may absorb the increase. If they don't, then higher paid workers may subsidize those who are paid less.
What will not happen is that entrepreneurs will operate businesses at a loss. Only governments do that.
Wait, you are not making sense. 4 emp. @ $7/hr is $28/hr. 1 emp. @ $15 is $15/hr a $13/hr savings.