Complex sentence: Operational risk is, nonetheless, manageable as to keep losses within some level of risk tolerance (i.e. the amount of risk they one is prepared to accept in pursuit of his objectives), determined by balancing the costs of improving the systems against the expected benefits.
Split into simpler sentences: Operational risk is, nonetheless, manageable as to keep losses within some level of risk tolerance (i.e. the amount of risk they one is prepared to accept in pursuit of his objectives). Such tolerance is determined by balancing the costs of improving the systems against the expected benefits.