Perp from platinum box

Either my luck is bad or it's just unfair. I've had friends who spent around $200-300 on keys and then around 200 plat boxes till they get perp. I'm already around $400 in and 300+ plat boxes in and no perp... smh it's hard not to stop, especially when barely anyone farms perp these days so I feel like it's necessary to do this. What would you prefer? Farm for months for perp for free, just takes time, or risk dropping money till you get perp through the box. Is there an actual percentage of getting the perp and I feel like some accounts are luckier than others.