BulkPricingUpdater (Bulk Pricing updater) in WHMCS 5 and 6 is an Addon which helps with bulk updating prices of the domain names of the WHMCS users/clients.

Alas it has wrong descriptions that do not allow safe pricing updating and developers are lazy to do anything with it wasting money and time of the WHMCS administrators.

So here is what to be careful about:

1. "Registration Period" dropdown menu - run the tool several times for different registration periods
2. "Domain Addons" tickboxes - tick all these tickboxes, else you will miss some domains
3. "Current price" - i keep it empty
4. "Currency" i keep it default currency USD, but for multiple currencies, you have to run the tool one more time for each additional currency x each additional "Registration period".
5. "New recurring price" - enter new price including decimal dots, example: 12.00
6. "-OR- Increase Pricing By" - i leave this empty

NOTE: bulkpricingupdater does not care about multiple registars, it will reset price for all! So it may be needed to then check clientsdomainlist.php and display domains registered via expensive registars and manually rise the prices.

Make sure to check client|s domains if the changes was successful: https://yourdomain.com/admin/clientsdomainlist.php

Hope that helped a bit.