As Linctex said, "...overall cost..."
Now, factor in the worth (to you) of services like:
1) side-by-side comparisons on a parts desk,
2) Ease of returning cores-not just the cost to mail 'em back,
3) Ease of and ability to return something defective after sale and possibly after installation,
4) warm and fuzzy feeling you get from dealing locally,
5) SPEED of just fetching a part without delay,
6) catching up with neighbors etc.