Why can't I find any specific fare information for Arriva buses?

I'm interested in the 500, 510 and Greenline 724 buses, but there's
absolutely no information anywhere on the net about these fares.

Does anybody know the fares for Romford to Harlow on the 500, Harlow
to Stansted on the 510, and Heathrow to Harlow on the 724?

Thanks for the help,
Victor