Lithium ion batteries are far cheaper now at a consumer level than they were thirty years back.

EDIT: I'm actually surprised that a higher proportion of laptops today don't ship with 100 Wh batteries. Go back some years, and shrinking the battery had a much larger difference in cost than it does today. The larger battery gives you longer battery longevity (makes it more reasonable to charge to 80%, say), can be used to make a laptop run more quickly, can power more devices. The only drawback is weight, and it isn't that heavy.