It’s double the regular fee if you use a bot run by someone taking a cut before MARA takes a cut with Slipstream….Libre Relay should get you mined with 1 sat/vB no problem (used to be F2Pool ran that, no idea what they do now but generally they’ll mine anything).

Your assumption about delays driving fees up only holds if those transactors are incredibly time-sensitive. If they aren’t (which is true of most of the inscription nonsense people) then it’s all one market - There is N weight in block space created in a day and only maybe 3% of it is restricted to non-inscriptions (or whatever). The inscription people will just get into the remaining 97% of block space that is now slightly less full because the filtooring hashpower took somewhat lower fee non-inscriptions.

There’s some edge cases around if the 3% of filtooring miners find a few blocks in a row so the prevailing feerate is somewhat lower in their blocks than others, but with so little hashpower it won’t happen.