To be honest, the biggest hassle in the certification process for me is making the map, esp. the S/F detail, rather than the ride itself, which I often find enjoyable (assuming the weather is nice).
Since I make all my maps electronically, all I have to do is modify the date(s) and any landmark descriptions that may have changed and it's ready to go.
That said, I wouldn't do a re-ride for next-to-nothing - probably not as much as a from-scratch measurement, but more than a nominal fee. And I wouldn't be surprised if some race directors, especially of small, shoestring budget events, decided to forego remeasurement to save money.