Sending a monster to the Graveyard for “Altar for Tribute” is a cost.
You can select a Token Monster as the cost for “Altar for Tribute”, but you won’t gain any Life Points because Tokens are taken off the field instead of going to the Graveyard.
You can send your opponent’s monster that you control to the Graveyard as the cost for “Altar for Tribute”, and you would gain the Life Points.
Netrep Rulings:
“Altar for Tribute” does not Tribute the card it affects.
“Altar for Tribute” does not destroy the card it affects.
Tokens chosen as the Tribute for “Altar for Tribute” will not increase a player’s Life Points as the Token will not go to the Graveyard.
Sending a monster to the Graveyard is an activation cost for “Altar for Tribute.”
If “Banisher of the Light” is active on the field when “Altar for Tribute” resolves, the player who activates “Altar for Tribute” will not gain Life Points as the monster does not go to the Graveyard.