But the prices come out as follows:

(3)
Monthly Basic Season
Hertford East to Liv St
£224 (first month) then £194 thereafter

(4)
Monthly Basic Season + Travelcard Addon Zone 1
Hertford East to Liv St
£313.10 then £283.10

(5)
Monthly Basic Season + Travelcard Addon Zone 123456
Hertford East to Liv St
£389.20 then £359.20

Now, unless I'm missing something, (5) and (2) offer what looks like the
same ticket, but rather than being "a discounted price" it would appear
to be the best part of £80 dearer.

Likewise, (4) and (2) are virtually the same price, but the latter
includes Z123456 rather than just Z1.

Can anyone help me make sense of this?

There is a further complication, which is that to get to Covent Garden,
it's much quicker, easier and less stressy in rush hour to change at
Tottenham Hale than Liverpool Street, but this option is not offered by
either of these season ticket pages. Does such a thing exist?

I'd also consider mixing a season ticket with a PAYG Oyster if this
looked like a better option.

Sorry for the rambling length - hope it makes sense (which is more than
I can do of One's website!)

Cheers

dave

With the Season Direct tickets, you are paying twice for usage within
the zones. Ideally the ticket should be to a boundary zone station,
but I can't get the website to offer me any.