SQL Server scalar function vs. subquery execution plan analysis

Can anyone help me understand the SQL Server execution plan for the following queries?

I expected the subquery version (Query 2) to execute faster, because it's set-based. This appears to be the case when runnning the queries independently - marginally - however the execution plan shows the query costs as 15% vs. 85% respectively:

//-- Query 1 (15%) - Scalar Function
SELECT 
    gi.GalleryImageId,
    gi.FbUserId,
    dbo.GetGalleryImageVotesByGalleryImageId(gi.GalleryImageId) AS Votes
FROM 
    GalleryImage gi

//-- Query 2 (85%) - Subquery
SELECT 
    gi.GalleryImageId,
    gi.FbUserId,
    (SELECT COUNT(*) FROM GalleryImageVote WHERE GalleryImageId = gi.GalleryImageId)
FROM
    GalleryImage gi

What am I missing here; does the execution plan skip over the cost of the function? Also, any suggestions as to whether either of the above would be better served with a CTE or OVER/PARTITION query?

Thank you in advance!