Seems expensive,

For me the "Big Five" has always been "Black"!

Would try a "White" however if given a chance.

Note also, the "assumptions" above are just that "assumptions" ie small pens.

Why would a parks rhino have to have been raised in a small pen?

They've been breeding in the wild for decades. I remember rhino (not white but black) programmes in Zimbabwe hunting areas in 1993. Almost walked into one, one night.