All I can say is....sometimes when the last 5 are 198.5 and now the game is 187, there is a reason

.
Don't always play with averages in mind...Vegas knows all that, they are not tossing out an arbitrary number. Kinda like 0-5 team going against 5-0 team, and line is only in 3-6 pt range....0-5 team will cover the spread I would say at least 75% of time.
Statistically though this is not far off...in fact, this is the highest line Denver has seen at home so far, check out the totals so far:
177
181
167
181
166
167
169
164
176
178
177
177
Average Denver line at home this year is 173-174
Average Dallas line on the road is 196-197
Average those and you are talking 184 range.
I doubt Joe Public knows that 181 is the highest line Denver has seen at home. Let the public hit the over some more and you will get better value.
Just my $0.02.