I did some experiments and found out batchTransfer can save 5% transaction cost for 3 recipients a batch, roughly 35% for 7 recipients a batch and up to 67% for 14 recipients a batch.
# cost per recipient for 3 recipients
(39257 - 37187)/39257
# cost per recipient for 7 recipients
(39257 - 25583)/39257
# cost per recipient for 14 recipients
(39257 - 12970)/39257
The gains seem to be fairly convincing.