Yep but they are now well above parity. Off the top of my head a report out recently found the average fare to be 10% above other London area TOCs on similar distances. Anyone remember reading that and got the link? I will try and find it as bloody google keeps bringing up todays fares announcement on searches. I need to find it, but I don't think it included HS1 and was a decent independent, thorough like-for-like comparison.
That may well be true; I think the increases have gone on beyond the original intention. I looked at a couple of fares in Kent over the same distance (37.5 miles): Tunbridge Wells to London Bridge (£20.10) and Maidstone East to London Victoria (£20.30) and compared it to the nearest difference on the GEML, Hatfield Peverel to London Liverpool Street (39.3 miles and £20.40). It is a little more expensive (53.9p a mile compared to 51.9p), but it's not like it is tremendously different.
Is Witham (the nearest large station) more well off than Maidstone and Tunbridge Wells? I think not.
Other lines may be getting a better deal, but I'm not convinced that Kent has been singled out for particularly harsh treatment on the fares front.