Off the top of my head:
$20-30 - Old Forester, Four Roses, Elijah Craig, Makers Mark
$30-50 - Woodford Reserve, Knob Creek, Basil Hayden, various small batches and single barrels, especially Elijah Craig and 4 Roses.
Over $50 - Bookers, Bakers, Woodford Double Oaked, Wellers 12, Makers Mark Cask Strength
I've had some of the way over $50 stuff, there's definitely a diminishing return. I drink Booker's on my birthday. A bottle of Makers Mark Private Reserve I bought at the distillery for $80 is the best bourbon I have ever had, and I wouldn't likely spend more than that to try to find something better, I'd just by another bottle of that specifically.
But if you are ever in Kentucky, try Very Old Barton. It's dirt cheap and really good.