Anderson said the Tiwai Point aluminium smelter renegotiation and the Greens/Labour policy announcement had wiped nearly $1 billion off the value of the company.
Before those announcements he believed the company was worth about $5.5 billion.
"I think what has changed ... is they [the Government] have come to the realisation they will have to discount more heavily to get it away."
The discounted value comes on top of incentives announced on Tuesday, including the two-stage payment plan and a capped share price for retail investors.
James Smalley, a director at broker Hamilton Hindin Greene, said there needed to be a significant allowance built into the price for uncertainty, given the potential for a change in government at next year's general election.
"The added risk around political change - that could be huge. Quantifying that is quite difficult."
Smalley said the revaluing of the asset would have occurred regardless of whether the company was going to be listed.
He said the Government had to meet the market in terms of valuation because it was trying to sell a large asset within a specified timeframe.
"To a certain degree that weakens the seller's position and strengthen's the buyers'," he said.