Yes well, changing you mind will always complicit things.
Obviously you have have to be happy with the thickness of the steel in the kit, thicker steel will cost more.
Speaking of Auctions, you can get second hand industrial sheds that are dismantled, complete or incomplete. Even if it's just the main frame, would be relatively cheap. Some times people will sell sheds cheap on a as where is basis, just dismantle and take it away, bit of work involved but could save a lot