Forgive my ignorance, but how does one take advantage of these travel deals?

Below is what was listed but when I visit the hotwire link it shows up $300 not $39, what gives?

From $19 each way! Denver, Phoenix, San Francisco, Vegas!

Travel dates: Varies with most from late January through May or early June!
Many more destinations at low one-way rates
Las Vegas $39 Jan 31-March 21
Denver $39 Jan 24-April 5
Phoenix $39-$59 Jan 21-March 29
San Francisco $52 Jan 10-April 19
Philadelphia $19-$38 Jan 31-March 21
Salt Lake City $55-$85 Jan 21-May 19
Portland OR $80-$105 Jan 21-May 20
Airlines: Frontier, nonstop or one connection
Typical fare: $300+

I found them here:

Go to http://flights.google.com
Click on Flights
Change the drop down from ROUND TRIP to ONE WAY
Enter DENVER and LAS VEGAS as the from and to cities
Change the calendar date to Jan 31
Then you can click on Price Graph and see the cheapest dates.

I see a bunch of $26 dollar and a few $19/