Labour state-owned enterprises spokesman Clayton Cosgrove said Dr Elder was getting a "big chunk of dough" from the taxpayer for doing nothing.
"Add that to his entitlement, add that to the two months' gardening leave, and I think the estimate is between $400,000 and $500,000 to leave.
"You've got to question the rationale around that, you've got to question those who said he's getting no more than his entitlement."
Mr Cosgrove said the payment was dressed up as a notice period, but was in effect "a golden handshake".
Solid Energy strategy and corporate affairs manager Bill Luff said the payment was for the balance of Dr Elder's notice period.
"Dr Elder confirms he will continue to assist the company during this notice period and beyond if requested and able to," he told Radio New Zealand.
He would not comment further, citing confidentiality.
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