SpaceX is a private company. Do you have a source for what their actual costs are for any of these projects?
Musk has claimed all kinds of things relating to costs with his other public companies, and none of it has been true.
You can afford to undercut profitable companies when you set OPM on fire.
You get what you pay for: with ULA, your payload makes it to orbit/space every time. With SpaceX, there's a significant non-zero risk of losing your payload, and that risk discount is what lets SpaceX undercut ULA. (That risk discount is also why SpaceX has to severely undercut ULA; the economics from a customer perspective wouldn't work out if SpaceX were only a small discount from ULA prices.)
Are you talking about Zuma?
There's "no explanation" because it was a classified launch, and the indications we do have are that it was an issue with a Northrop Grumman payload adapter.
ULA's perfect score is a bit of a cheat, as the rockets they launch were inherited. The first flight of the Delta IV Heavy, for example, was a partial failure... but happened before ULA's formation.