On Mon, 02 Apr 2007 20:46:55 +0100, Dave Newt wrote:

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?

I don't think you've made any mistakes; it appears the claim about the
price being "discounted" is simply false.

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?

Option (2) is the cheapest ticket that would allow you to do this.

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

Your options are (all prices are for 1 month and assume 22 working
days per month and return journey starting before 7pm):

Hertford Stns - London Terminals season £198.20
Liverpool St - Covent Garden PAYG 22 x 2 x £1.50 = £66
Total: £264.20, but this involves travelling via Liverpool St

Hertford Stns - Z1-6 Travelcard season £282.70

Hertford Stns - Tottenham Hale season £188.20
Tottenham Hale - Covent Garden PAYG 22 x 2 x £2.50 = £110
Totel: £298.20

Hertford Stns - Tottenham Hale season £188.20
Z1-3 Travelcard season £105.30
Totel: £293.50