with no ongoing costs
I think that there are costs, but they’re hidden. There’s a lost opportunity costs for every self vote. 100% self-voting is very effective in the short run (I’ve seen estimates in the 30-35% annual return range), but it achieves that at the expense of building relationships. If you’re not voting for and commenting on other’s posts, you might completely miss the chance to attract the attention of dolphins, orcas, and maybe even whales who might provide upvotes for years to come.