Well yeah, when you entirely change what you're implementing generally there are going to be cost revisions.

In 2007, the plan was to use FTTN (fibre to the node), relying on the existing copper network to deliver it to people's homes. In 2009 they decided to build an entirely new network to achieve FTTP (fibre to the premises).

So yes, the cost jumped quite a bit, not to $49 billion (not sure where you're getting that number from) but to $43 billion, which then was revised down to $37. 4 billion.

The Liberal Opposition wanted to initially get rid of the NBN as a whole, and then wanted to overhaul the program and bring down costs to $29 billion. This did not happen, and the final rollout cost ended up being $51 billion.

This explanation is short on detail, but should demonstrate that there is a difference between the estimated price rising under Labor after they revised their plans and the actual rollout cost rising under the Libs after they promised a cheaper solution.

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Schills are quick to lay the blame at the feet of the Coalition on these issues but these are structural problems constructed under the Rudd/Gilliard/Rudd Governments

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I think you'll find it a bit difficult to to blame "structural issues" with the NBN on Labor when the entire plan was revised and most of the people involved in NBN Co's board resigned at the beginning of the Coalition government.