Here's the average density of the standard woods:
California Walnut
Specific gravity = .60-.70
Bubinga
Specific gravity = .65-.80
Vermilion
Specific gravity = .65-.75
Purpleheart
Specific gravity = .75-.90
Western Flame Maple
Specific gravity = .55-.65
Eastern Maple (Bird's-eye)
Specific gravity = .65-.75
Lacewood
Specific gravity = .45-.65
Zebrawood
Specific gravity = .65-.75
You're right, the top laminate is only 1/4 thick, so while you will notice a difference in weight between the heaviest and lightest top woods, the neck and the main body wood will have a larger impact on the weight (and tone) of the bass.
Here's an example with the Essence bass. The original all-Maple Essence basses weighed about 8 pounds on average for a 4-string. My Essence is 10.75 pounds with a 7-piece Maple/Purpleheart neck, Cherry body and Kingwood top. This is in stark contrast to the 6.75 pound Zebrawood Essence in our showroom that has a Mahogany body, and a Mahogany, Walnut and Birch neck that feels like it is filled with helium!