This may be true in the UK, but in the US Steam games are price-competitive with shrinkwrap versions.
After all, you don't get any physical copies, which is something a collector may like.
The online features are also not too shabby - being able to join a friend's game in a single click is a pretty nifty feature that I use often.
Also, Steam generally gives 10% off for preorders, which is something brick and mortars aren't doing.