High quality graphene prices have been going down from being expensive to being estimated to be 1 euro cent per square centimeter by 2022. Currently, graphene is 10 euro cents per gram.
Here is a Rough Estimate on the costs of a graphene mesh space tube from the Earth to the moon -
HOW MUCH GRAPHENE DO WE NEED?
The distance to the moon from Earth is 238,900 miles.
There are 1.6 km in 1 mile, making the converted distance to the moon 384,472km.
The Distance from the moon changes due to the Earth's rotation, thus implying that we need something to stretch or shorten the tube at times.
We would need to test to figure out the right thickness of graphene necessary for the space tube, but if the tube was 20 meters wide (radius of 10m), it would require 24,157,100,000 square meters of graphene (the lateral surface area of the cylindrical mesh of r=10, going from Earth to the moon).
CALCULATING LATERAL SURFACE AREA OF A CYLINDER.
L= 2π x 10 meters x 384,472,000 meters
L= 24,157,100,000 square meters<
Let's say we timed by this by a 100 to make the mesh super thick (adding a 100 layers), and we get 2,415,710,000,000 square meters of graphene necessary.
HOW MUCH WOULD THAT COST?
One square meter of graphene currently costs 100 euros.
2,415,710,000,000 sq meters would cost 241,571,000,000,000 euros or $266,446,773,725,000. In other words, just about 266 trillion dollars. But the prices are expected to keep going down dramatically. By 2022, this cost could drop to 26 trillion. If this trend continues, the price will become "affordable" by around 2031.
2025 - $2.6 trillion
2028 - $260 billion
2031 - $26 billion
You can also make the mesh less wide and thick to start with and save money that way.