Doesn't seem too expensive to me, an old R&D Engineer who changed to Manufacturing Management 25 years ago. -------
In fact, the technology already exists. In 1975, the US Navy patented a device for producing "a powder contrail having maximum radiation-scattering ability." The powder contained a mixture of 0.3 micron-sized titanium dioxide pigment particles coated with 0.007 micron hydrophobic colloidal silica and 4.5 micron particles of silica gel. The purpose of the apparatus was "to generate contrails or reflective screens for any desired purpose."
The Welsbach Patent proposed using "very fine, talcum-like" powder of 10 to 100 micron-sized aluminum oxide to produce a "pure white plume" in the sky.
In a May 2000 draft report submitted to the International Panel on Climate Change (IPCC), an expert panel chosen from among 3,000 atmospheric scientists, concluded that Teller's scheme might work. But the IPCC warned against unpredictable upsets of the atmosphere.