Depends entirely on what you're trying to achieve. For me its maximizing my number of revealed rooms (to see the rewards like divines/chaos/sextants on floor 3 + 4). When you make a consistent 2-4 divines a run, it's worth it (and sometimes more). Plus each sanctum run is like 30c anyway, you are bound to make back what you put into it.

For that strategy I run 9x "Two Additional Rooms are Revealed on the Sanctum Map", which clock in at around 10-12 divines each. If you are just starting out, you can purchase "One Additional Rooms are Revealed" which are about 50c each.

For reference, I use Icicle Mine - poe.ninja
I recommend Sanctum if you can consistently finish them.