since mythic weapons are extremely tied into nyzul island plot wise, why not make it so that progressing deeper in nyzul isle lowers the Immense Alexandrite requirements?
make nyzul go down the full 500 floors, each 100 floors progressed lowers your alexandrite requirements by 5000 alexandrite totaling in a 5000 Alexandrite Final requirment. this would make mythics more redialy avalible to players, also remove the negative returns after floor 100. Nyzul points should increase to the point of always yielding considerably more points then what one has spent.
Additional suggestions
1) allow for alex pouches to drop off of Eliminate enemy leader, and target monster floors.
2) A reward for "Kill all/family" floors in the event of a swift execution of all mobs. causes a chest to randomly spawn on the next floor containing Nyzul Points and alexandrite. spoils are awarded to all party members when chest is opened.
3) A reward on lamp order floors, provide a 1~5 minute time extension for an
accurate solution to the Order (bonus = 5-1 minute per failed attempt)
4) A time reward on single lamp floors for swift resolution. 5 minute bonus - 1 minute per minute.
5) Instant teleportation on completion of floors other then "free floor"
6) Provide bonus spoils for every floor over 5 floors progressed in a singular run ( therion ichor, Nyzul Points, and Imperial Standing)
Notes:
1) allow only up to a 30 minute time extension
2) Failure to abide by a secondary restriction (no gears aggro, or death) results in loss of any bonus for that floor.
3) only allow #6 to function post floor 101.