Magmi Plugin For Importing Group Prices
(base code / forked from tim-bezhashvyly/magmi-grouped-price-plugin)
This plugin allows to import customer group prices.
The column format for customer price groups is group_price:customer_group, where customer_group is your customer group name.
Multiwebsite functionality
You should have a websites column with comma separated website codes (e.g. com,net) in your import file.
Use the same ordering in the group_price column (but with pipe (|) as separator:
e.g. group_price_for_com_website|group_price_for_net_website.