This may be unique to this provider - I travel frequently to Las Vegas. They have a large rental car facility about 3 miles from the airport, and then there are several "off-airport" companies with lower rates for which you have to take a second shuttle. There's one in particular that I use, Nu-Car, which is right across the street.

Last night I was looking for rates for an upcoming 4-day trip. I found a pretty good rate, about $28 a day all-in. I waited about 20 minutes to book it, and by the time I did, the rates for that company had skyrocketed to around $45 a day. In only 20 minutes.

This morning I looked again and it was now $25 a day. Needless to say I booked it before it ran away again.