Hello there Notafish
Well,as regards prices at Covent Garden.
They now go from £8.00(standing) up to (are you ready for this?)~
£204 for the best seats in the Stalls and the Grand Tier (equivalent to the Dress Circle in a theatre).
Of course most of the cheap seats go very quickly,the only way to ensure you get such seats is to be on the mailing list,or to become a "Friend of Covent Garden"(which requires annual membership).
The "Friends" get first whack at the seats,followed by persons on the Mailing LIst.
However,neither get any seat price reductions.
This is then followed by the General Public booking.
The Don Carlos I saw was (If I remember) June 2008.
Now I am going to annoy/sicken you.LOL
As a previous staff member of Covent Garden,I can get free seats from colleagues or(if there are any) the box office.
Sorry!
I have also posted this in CB in case you don't look here!