Can I pay to rank higher or be featured?

No. There is no sponsored slot in the rankings and no vote packs. Where a product sits in a list depends on how many people upvoted it.

The Featured section on the home page is separate: those products are picked by the Upfynd team, and featuring one does not change its upvotes or its place in any list.

That is the point of the directory: a list you can buy your way up is not worth reading.