From my observation it is hard to get to 501 karma points by the karma gained from submissions than through comments. So for comments every 1 upvote equals 1 karma. But for submissions, god only know what is the conversion rate /s. I think there are many factor. But I think this mechanism is to limit people creating accounts and mass down voting anything they don't like. So it is trying to solve another problem. However upvote power should be limited for new accounts (I don't know if this already the case)

I might be biased in my perspective because I tend to focus on links that make it to the front page. It's true that many links end up languishing in obscurity.

I just think the level of effort involved is different. For instance, the person who posted the link to the study we're now discussing earned 199 points with far less effort than you put into replying to my comment. Many of the links posted are copied from Reddit, Twitter, Slashdot, etc.