They are doing a fair amount of added bonus for the HD DVD release. It's not an exact replica of the DVD release but in hi-def.
Besides, 5 DVDs = 42.5 GB (8.5*5). Last I checked, HD DVD can't hold that much and you're asking for hi def which is going to take up more room.
To cash in my CC rewards points for $300 in Circuit City gift cards to purchase a 360 or not: That is the question.