Since you mention that you live in a semi-rural area, one hugely important factor is the density of premises along a street. The less dense an area, the fewer potential customers you can "pass" by installing a new fibre cable down a street. Not all premises that you pass with a cable will want to sign up and pay for a fibre plan.
Construction can be made dramatically cheaper if it is possible to re-use existing infrastructure. This is important, as if you are laying underground fibre then the cost of digging new trenches (~AUD$100/m) is a huge component of the total construction cost. For example, when installing underground fibre, if there is existing underground duct with capacity that can be used then it is far cheaper to re-use that (~AUD$20/m) than digging new trenches. Similarly, if there are existing poles that can be rented then installing aerial cables (~AUD$30/m) is cheaper than digging trenches, but more expensive than using existing underground duct [1].
Another way to re-use existing infrastructure to reduce construction cost is to make use of existing cable, such as copper lines or HFC, instead of laying fibre over the full path from the exchange to the premises. The quality/speed of the connection will not be as good as a pure fibre connection, particularly if the existing infrastructure is old/degraded. These approaches are now being favoured in Australia's national broadband project [2].
[1] note that in the U.S. labour costs are lower than in Australia, so don't take these cost-per metre estimates too seriously. These costs exclude the cost of the fibre itself, which is typically a few dollars per metre.
[2] personally I think it is short-sighted to embark on a major infrastructure project and then try to save money by avoiding building the new infrastructure, and instead re-use the existing degraded infrastructure. These decisions were hugely influenced by political factors after a change of federal government, i.e., the old plan was necessarily bad and needed changing because the previous government started it.