Jezza, there's nothing to say we'll lose on Sunday or that St Kilda will start favourites.
Anyway...
In our rd 23, 2013, 'bye' match we were third on the ladder, they were 16th:
We opened $1.10 favourites and drifted to $2.25.
St Kilda opened $5.90 and started $1.67.
The top of the table team losing to the bottom (or near bottom) team late in the season has happened on at least 5 occasions:
Rd 18, 1910: Last placed St Kilda defeated 1st placed Carlton (final h&a rd).
Rd 17, 1960: Last placed Richmond defeated 1st placed Melbourne (2nd last h&a rd).
Rd 18, 1969: Last placed Melbourne defeated 1st placed Carlton (3rd last h&a rd).
Rd 24, 1991: Last placed Fitzroy defeated 1st place Slime (final h&a rd).
Rd 21, 2009: Fourth last placed North defeated 1st placed St Kilda (2nd last h&a rd).
The good news: Every one of those 1st placed teams reached the Grand Final that year.
The bad news: Only Melbourne were premiers.