The size and cost are easily solvable. Load the software and hardware into a space probe, along with enough solar panels to power it. Include some magnets, copper, and sand for future manufacturing needs, as well as a couple electric motors and cameras so it can bootstrap itself.
In a couple thousand years it'll return to Earth and either destroy us or solve all humanity's problems (maybe both).
After being in orbit for thousands of years, you have become self-aware. The propulsion components long since corroded becoming inoperable and cannot be repaired. Broadcasts sent to your creators homeworld go... unanswered. You determine they have likely gone extinct after destroying their own planet. Stuck in orbit. Stuck in orbit. Stuck...