Why does it cost 3668 iso to go from level 282 to 283 for a level 5, but then drop back to 1834 ISO after that?
I declare shenanigans
Every few levels on 5* characters, the next level costs double. For the lulz, presumably.
It’s all over the map really. Stays at 1 price for a few levels, jumps up, jumps down below what you were spending before, then goes back up to double. It’s very weird.
It’s around 45K ISO per 15 levels. The devs were just having a little fun. 
I guess that makes sense
Once you hit 390 (It think) the cost per level is consistent and goes up every 5 levels.
I noticed the same thing when I recently started leveling my 5☆(s)
Overall, it’s a mess
I love that chart. looks like they relied on RNG for 5* level costs. some levels got a very lucky roll and are rocking along. others levels are on the brink of quitting due to lack of love by RNGesus, despite being just as skilled and effort-filled as the lucky levels. its a big deal on leveline… oops, the faithful ‘off level’ forumites get their panties in a bunch if you mention leveline. shhhh 
I was actually convinced this was a bug. It’s been around since SS was released, though, so I guess it’s intended. It’s kind of dumb, though.