$2:
Cellar
Secret Chamber
Duchess
$3:
Masquerade
Warehouse
Village
Workshop
$4:
Baron
Coppersmith
Gardens
Remodel
Noble Brigand
Horse Traders
Bureaucrat
Spy
$5:
Soothsayer
Duke
Counting House
Council Room
Festival
Rabble
Count
Jester
Cartographer
$6:
Hunting Grounds
I think that's a 25 card set, which hopefully looks fairly normal, although there's probably some oddities in it I didn't pick up on. And if this were the only 25 card available in Dominion, or were the first 25 cards available, I think this would often have bigger decks being preferable for various reasons - Gardens is a big one, along with things like Counting House, Coppersmith and Baron to key off of those cheaper cards. On top of this, there's no good trashing - Masquerade and TfB are there, but nothing that can trash multiple cards per turn. There is however a number of sifters, which will make slimmer decks relatively less valuable. There's two alternate VPs, each with support, and combined with the things comboing with cheaper cards, perhaps this would lead to the more valuable cards seeming relatively less good?
Of course, all these things will depend on the card which appear in the game, but if this were the first set, I suspect the 'general' ideas people would have would be very different to what they are now.