Login register snippet &persistParams

how does this work? Besides a very short and vague explanation on the docs no one seems to know.
what i'm looking for is a way to transfer all the form values to a confirmation page and have so far come up empty.

I've tried:

&persistParams=`{"price":"47"}`

which puts a GET parameter in the redirect page's URL

also tried:

&persistParams=`1`

Even though the default is an empty string.
I would appreciate any assistance.
https://community.modx.com/t/login-register-parameter-persistparams/2003