Two-inch black gaffer's tape over the logo on the back of the synth (or 4x12 guitar cabinet) = not free.
No tape over logo = free or deeply discounted.
If you have a band with any kind of exposure, manufacturers will typically offer discounts, often significant. Larger bands will get instruments for free under endorsement deals. In general, famous people get TONS of cool stuff for free (a single Instagram photo or tweet with a star holding/using your product can literally be worth millions). I know first-hand that Mesa/Boogie sold guitar amps at over half-off to a relatively unknown band, but whose lead-guitarist was on a reality TV show (their publicist offered to get one for me).
I'm pretty sure Orianthi got her Engl guitar amps and PRS guitars for free (below). Now, she's an Orange Amplification "ambassador."