If the chassis is straight, both airbags are installed and it looks well put together, I'de pay $20k. There are many salvaged tittle supras (which have been repaired with a new clean title) which are properly done.
Make sure the chassis is straight, body panels line up. Check the shock towers and look for the impact subframe beams for any bends/kinks. If it was hit hard, the subframe is tough to "push" back foward, and you'll see a dent in the subframe near the oil filter (or the other side as well).
People say the resell value drops, but its a Supra. If a Supra is hit over and over, but fixed over and over, in and out of salvage titles and what not, yet the car keeps coming back straight, clean, aligned with all body panels looking proper, I don't see why the car would go for less. The person who buys it for $10k will have a Supra just as good as one who bought it for $30k. I think its more of a "cop out" when folks mention it. If your selling a salveged Supra to a supra owner who knows (or will know) a Supra in and out, the resell value shouldn't drop.