Michael Hoffman wrote:

How much does a Young Person's Railcard-discounted Travelcard cost in
2007?

It's still £4.80 - see page F3 of the National Fares Manual.
http://www.atoc.org/retail/_downloads/NFM95/NFM95_Common_F.pdf#page=3

Note that

Can you only get the Zones 1-D travelcard?
What if I buy from a National Rail station?

National Rail ticket offices issue it with zones 1-6 validity. At
Underground ticket offices it's issued as zones 1-D - i.e. LU throws in
zones A-D for free. This is not documented in any passenger facing
literature, but many posters have reported it in the past on utl


Anyone ever had trouble getting an LU ticket office to sell them such a
thing?

Past posters on utl have suggested that it can be difficult to obtain
from LU ticket offices. It's quite possible that some LU ticket office
staff aren't clued up on it's existence or may not be aware of it. I
imagine that LU doesn't put much effort into communicating info about
this ticket to it's ticket office staff.

Why doesn't LU advertise it?

It's a Train Company ticketing product, not an LU one. AFAIAA LU has
never advertised it or even acknowledged it in public literature. Plus,
nowadays, LU is busy promoting Oyster, and definitely not promoting
paper tickets!

Even ATOC doesn't seem to know the rules - see FAQ no. 14 on the YP
railcard website:
http://www.youngpersons-railcard.co.uk/faq.htm#14

-----
14. Can I use my Railcard for tickets for travel on the London
Underground?
All discounted rail tickets bought using your Railcard routed 'between
London termini' are valid for cross-London transfer on the London
Underground. Off-Peak Day Travelcards (All Zones only) are also
available, subject to a minimum fare. Please note, however, that you
cannot use your Railcard to obtain a discount when purchasing tickets
from a London Underground booking office.
-----


Note that the Network Railcard also enables holders to buy discounted
Day Travelcards for themselves and up to three accompanying adults and
four children. However monday to friday it cannot be used until 10am,
and it also has a weekday minimum fare of £10 - making it useless for
buying in-boundary Day Travelcards except at weekends and bank holidays
(when these weekday rules don't apply).

Sorry for all the questions.

That's what this group is all about