Taking down notes here :
Batamfast Online

Above was tabulated from the Batamfast online ferry ticket purchase system (all tax inclusive),hehehe...weird timing to go and leave Batam tho,but still...its fine for me since the destination would be via Harbour Bay.
And below is the promo they have for Senior Citizen,hehehe...i think after everything in,it would cost around S$32 plus minus (all ferry terminals).
...and i saw one here from Majestic Fast Ferry,but not going Harbour Bay.
Gives me the impression,these ferry companies are fighting for senior citizen business,hehehe...
Not so sure about Sindo Ferry, i saw their ongoing NTUC Silver card's S$10 off promo tho. The rest of the other cards like NTUC card,Passion card and MDIS card gives a $5 off for 2 way ticket, and finally...their senior citizen promo,hehehe... (but you will need a Passion Silver card) Adds up to be around S$32 plus minus tho.
* Above were just notes for my future Batam reference and analysis.
** Sindo and Majestic dont go Harbour Bay.
*** Horizon Fast ferry do not have a promo at the point of this post