Historically, the U.S.'s big launchers fly seldom enough that their costs are dominated by annual upkeep of facilities and staff, not by the actual cost of each launch. The expensive part is maintaining the launch capability, not actually conducting launches.
Foul-ups in testing are not uncommon, especially when the test setup is being tried for the first time.
One of the headaches of high-tech test programmes is having to debug the test arrangements before you can start debugging the things you're trying to test.
Sometimes a malfunctioning test setup actually gives the tested system a chance to show what it can do in an unrehearsed emergency. During a test of an Apollo escape system in the 1960s, the escape system successfully got the capsule clear of a malfunctioning test rocket.
