Persona 4 summon costs wrong

[arantius]

Looking through my compendium, trying to find bare (i.e. not leveled/fused with extra skills) personae I see (I have 15% discount in game, normal difficulty):

• Izanagi Lv 1, Comp. ¥1,829, Calc. ¥2,300
• Pixie Lv 2, Comp. ¥1,854, Calc ¥2,507
• Mokoi Lv 14, Comp. ¥3,741, Calc ¥9,203
• Vetala Lv 19, Comp. ¥5,196, Calc ¥14,288
• Nozuchi Lv 27, Comp. ¥8,289, Calc ¥25,232

The formula for calculating cost was carried over from Persona 3, and apparently doesn't apply to 4? Those are off by way more than 15%.

[matrinox]

Also some are just wrong in terms. For example, Eligor + Oberon (lvl 12) is 15,094¥ but Eligor + Orobas (lvl 8) is somehow more at 17,313¥. I suggest an easy fix would be to reset the values using a simple linear formula based on level. Then future PRs can make the costs more accurate.

[arantius]

The current formula is just one line:

https://github.com/arantius/persona-fusion-calculator/blob/gh-pages/app.js#L92

If you want this fixed, the best first step would be gather more data points (what do various personae at various levels cost, without extra level ups or fused skills?), then the second would be proposing a formula that matches better. The five points I've got above are non-linear. If I do

cost = (7.5 * level * level) + (40 * level) + (1800)

It's pretty close (never off by more than 100). But some higher level data points would be necessary to build confidence.