They combat this fairly smartly: the fine starts at $125 and doubles with every incident, up into the thousands. This was the case before this toll road, circa 2013 ish.
When the I-66 HOV lanes originally opened, there was a problem of some percentage of drivers being willing to risk an $X citation (and the delay while being written up) every few months in exchange for using the road every day.
The solution that VA put in place to combat that is that the HOV violation citation not only has a money cost, but second or subsequent infractions within a five year window result in assessment of points [1] against your drivers license. Only a small number of points [2] is necessary to risk losing your license.
