Ryanair does not have a public image that would allow it to survive a serious accident - the passengers would walk away in droves. As a matter of corporate survival, they have to take safety seriously - and I am sure they do. I can think of many reasons not to fly Ryanair - but concern about safety is not one of them.
Safety is not about how much you spend - it is about how you spend it. And I would guess they have a pretty good grip on that issue too.