A betting line is not an indication of how much Vegas feels one team will beat another by. It is an arbitrary number (sure they use some metrics as a starting point) designed to provoke equal betting action on the favorite and the dog. Nothing more...nothing less.
Trust me, I am quite aware of that. However, with analytics having become much more mainstream in recent years, Vegas has adopted it as the main means of setting a line they believe is best suited to get equal action on both sides. For example, if Vegas blindly throws out a line of Team A -4 when the KenPoms, Sagarins and other CBB analytic sites project Team A to win by 8-10, guess which side the majority of the money is going to flow.
Imagine running a sportsbook and having to post a line on each of the 5 Ohio Valley Conference games that are being played on a given night with the goal of making the line accurate enough to draw close to even action on both sides of every game. Do you think they have some OVC expert projecting what the lines should be, or do they use analytics as the main driver for the opening line? It's the latter.
Analytics has completely overtaken every aspect of sports, and you'd be a fool to believe that Vegas doesn't depend heavily on it in their linesmaking. This is because the only way to be a successful sports bettor over a long period of time is to have an analytics based system more accurate than the linesmaking system. Vegas knows this and isn't going to allow anybody to have that edge.
If you want to confirm this for yourself you can. There will probably be in the neighborhood of 75 lined CBB games this Saturday. Just buy a subscription to KenPom.com and check out the score projections for this Saturday's games on that site. Match them up with the point spreads and you'll see the vast majority of the lines are within a point of the KenPom projection. There will certainly be exceptions, but again, analytics drives the line.