The prison uses your own history as the bars. Every day you stay, you add another bar to the cell, making leaving feel more impossible. The logic is inverted: Because you have invested so much, you feel you cannot afford to walk away. In reality, because you have invested so much and nothing has changed, you cannot afford to stay.
Jokes about prisoners who got the "cheapest cell" available. Minimal Confinement: One Bar Prison
: Modern designs often include a safety pad at the top of the pole to prevent injury from unintended movement or loss of balance. Common Variants & Accessories The prison uses your own history as the bars
Here’s a helpful review of One Bar Prison (assuming you’re referring to the novel by Andrew Diamond—if not, let me know and I’ll adjust): In reality, because you have invested so much