Tech has done wonderful things to keep costs down, but it's a lot tougher to get that barrel of oil now days. I think there are, at least to some degree, costs being offset by increased risk. Deepwater horizon is a pretty obvious example. Groundwater contamination from fracking is another. I think the price per barrel has been on a steady downward trend, but I'd bet that including the environmental impact just from accessing (not burning) oil, we're paying more. I'm not aware of any such study.
In any case, we're the first, but also last technological civilization to use oil. If a wizard waved a magic wand, and we were suddenly sent back to a 1700's level of technology, i don't see how we'd be able to get much oil at all. It's not bubbling up out of the ground anywhere anymore. The easy stuff is gone. there's no way to get the hard stuff by hand.