7.5 metric tons is well within the weight limit for a Falcon 9, so add about $57m for the launch costs for a total project cost of probably around $500m.
That puts it in the realm of the Voyager probes for total cost.
Thank SpaceX for slashing launch costs and me for not factoring in much of a second stage to boost that mass out of orbit.
But I was also extremely generous with the thickness in the first post. In real life they would almost certainly be closer to .05mm than 1.2mm, and probably not made out of solid gold.
The point was to show that even with some rather pessimistic assumptions the project was within human scale and even had some precedent.
Yeah, it's all within the realm of possibility, with too many unknowns (eg, what is a realistic information density) to really easily say how easy or hard it is.
Re: Falcon 9's, Voyager was lifted on a Titan IIIE, which had a LEO payload of 15,300 kg, compared to 22,800 kg for the Falcon 9 to LEO. Assuming Voyager was near the capacity of what could be ejected from the Solar System by a Titan IIIE, you'd need to send up ~7 Falcon 9's to Voltron together in orbit.