How much are we supposed to pay for the re-registration if not applying for the renewal of the EAD?
Following is what I sent in the package (which was returned to me) -
1. Form I-821 (for re-registration)
2. Form I-765, did not select any of box at the top
3. Money order for $135
Since I was not applying for the renewal of the EAD, I thought I was supposed to pay $135 ($50 for i821 and $85 for biometrics).
In the return package, they have included 2 rejection letter--one for i821 and the other for i765. The reason for rejection in both is invalid fees amount.
It's been indicated that I can resubmit the application, however, the correct amount for the fees is not mentioned.

You over paid!

$85 for biometrics should be sufficient if you aren't renewing the EAD, provided that you
put check in 2.b of I-821 form.

TPS re-registration is free, check the UISCI document below, page 7 > no 2 under section "What is the filing fee?"

https://www.uscis.gov/system/files_force/files/form/i-821instr.pdf