OutputGroup::m_value is the true value, not the effective value,
so use the true values of the outputs, not their effective values.
This is a backport of [[https://github.com/bitcoin/bitcoin/pull/17458 | core#17458]] [1/2]
https://github.com/bitcoin/bitcoin/pull/17458/commits/9adc2f80fc14f11ee2b1f989ee7be71b58481e6f#