You don't think there is a big difference between 15 years in prison and the death penalty?
You still have a lot of time left in life after 15 years so it is major difference.
US violent crime has plunged over the last 40 years, and the murder rate has been chopped in half since 1980, all the while death sentences have declined to ~45-50 year lows (there has been roughly a 90% reduction in new death sentences since 1999). The dramatic plunge in new death sentences over two decades hasn't coincided with any uptick in the murder rate or violent crime.
There's a theory that violent crime has plunged over the last 40 years because of leaded gasoline being phased out: the lead was in the air and environment and giving everyone low-level lead poisoning.
But (approximately) nobody commits a crime on the assumption they will get caught, so it pretty much doesn't matter what the punishment is. The way to move the needle is to change the assumption about getting caught. The closer that tends towards guaranteed, the less chance people will even make above calculation in the first place.
Invert it: if faced with the death penalty, how much effort would you expend to get it commuted to 15 years?
Here’s the right way to look at it: what do you consider to be the acceptable odds of being imprisoned for 15 years while traveling to a foreign country? And what are the acceptable odds for being killed?
I don’t have a concrete number for either one, but they wouldn’t be much different.
Consider also that your odds of dying in a traffic accident are much higher than your odds of being executed on false pretenses by the state in most places (especially China, where they’ve only recently decided that wearing seat belts is something you should actually do, and the annual per-vehicle fatality rate is almost 10x that of the US), so the added risk from executions is hard to even detect.
Sure, the acceptable odds for both are similar and very low, but the outcomes are vastly different. Once my dice roll has bought me into contact either one of those possibilities, I am passionately invested in making sure it's 15 years in prison.
(Edit: such thinking is of course why plea bargains work and are used so often by prosecutors in the US.)
My point isn’t that they’re basically the same in all aspects, it’s that they’re basically the same in terms of their input to the decision of whether to travel to a given place.