As Anthony said, it's all about how desireable an animal is.
Quite frankly, I think those trachs are amazing, and unfortunately rare animals. $5000 does seem like a reasonable price to me, all things considered. I most certainly can't afford it, but I would love to see more people working with them.
On the same hand, I think those very rare and highly unique geckos are worth far more than a white ball python...but you will see people paying a price for those you could purchase a house with...based on scale color alone. But people still want them, and WILL pay...hence the price.
Now, I think the difference between the $5000 trach, and a $5000 crested is HUGE. I'm sorry but a) the color is not bright green, it is olive. And b) it is relatively common.
And most people know this, wouldn't pay, and think it's outrageous.
So again...desireability.
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I am highly prized for my meat.