I was making a journey last week from Tottenham Hale to Stansted
Mountfitchet.

As I had a Z1234 travelcard, I asked for it to start from Boundary Zone 4.
One WA Ticket Machine Operative in the LU gave me the said ticket.

I then had a playaround on the Ticket Machine by Platform 1, and found it
was cheaper to get a ticket from Tottenham Hale, rather than Bound. Zone 4.

Any ideas why it is cheaper ?