From the Twitch Documentation:

Quote:
msg-param-sub-plan (Sent only on sub or resub) The type of subscription plan being used. Valid values: Prime, 1000, 2000, 3000. 1000, 2000, and 3000 refer to the first, second, and third levels of paid subscriptions, respectively (currently $4.99, $9.99, and $24.99).


Therefor, you can just tell your script what to do with the values.

Example 1:

Code:
IF ($msgtags(msg-param-sub-plan).key == 1000) VAR %sub-plan $chr(36) $+ 4.99
ELSEIF ($msgtags(msg-param-sub-plan).key == 2000) VAR %sub-plan $chr(36) $+ 9.99
ELSEIF ($msgtags(msg-param-sub-plan).key == 3000) VAR %sub-plan $chr(36) $+ 24.99
ELSEIF ($msgtags(msg-param-sub-plan).key == Prime) VAR %sub-plan Prime


Example 2:

Code:
VAR %sub-plan $replace($msgtags(msg-param-sub-plan).key, 1000, $chr(36) $+ 4.99, 2000, $chr(36) $+ 9.99, 3000, $chr(36) $+ 24.99)