Depends on the world-
en1-en7/8 are pretty established, so if you have a high friend you'd probably get it for like below 100 FPs.
en8/9-en12/13 Between 250-500, I guess.
en13-15 Prepare to pay a month of FPs.(800-1500)
en16 I am on this world, the highest is Future. Don't bother.