Yes, the development would have been elsewhere.
Anyways St-Albans is like Oakleigh, it's a community hub, with shops and retail. If the road bridge was built like before the development, there would be no local amenity and the shopping strip wouldn't exist.
There are examples of similar road bridges having been built before development, look at the outer section of the Craigieburn line.
And speaking of Craigieburn, there is a bridge over Craigieburn bypass which cost about $36,300,000 in today's currency and the price tag included that of a lot of sculptural noise wall, landscaping and a light show.
If you look further back, a lot of embackments and trenches were built to remove level crossings. There are about as many elevated track as there are trenches. Believing there are more trenches than elevated track is not reasonable. Embackments are part of Elevated rail...I don't think of a railway on an embankment as elevated rail, the ground level on an embankment is higher than to the sides.
Even the so called "skyrail" has embackments, it just has more bridge, that's the only difference.No embankment, the ground level is the same as to the sides, just the tracks are above ground level.
Building a house is cheaper than that over expensive pedestrian bridge over the trench. It's not even a huge bridge and it costs 1 million. Just imagine covering the whole trench, oh dear that's many millions of dollars covering a trench.The one in Box Hill only cost $754,000, under a million. Also, I find it hard to believe a much bigger house would cost less than that. It doesn't need nearly as much material and as far as I can see, there are no engineering challenges in building a footbridge over a railway cutting with no supports in the middle.
That's why elevated rail is superior for connectivity, no-one can dispute this. it's just too expensive to cover a trench.And yet there didn't use to be any viaducts in suburban Melbourne, but plenty of cuttings and embankments, these being about equally common.