Does elreon jewelry come before or after %reduced mana cost?

Trying to calculate my eventual mana consumption.

Example: 30 base mana cost with support modifiers, one -8 elreon ring, 25% passive mana cost reduction.

If elreon jewelry is counted first: 30 - 8 = 22 * .75 = 16.5

%Reduction first: 30 * .75 = 22.5 - 8 = 14.5

I figure vipermagi or raics would know this immediately, Thanks!

Right, it's after multipliers and reductions to mana cost.

Which might be a bit counter-intuitive, considering flat values usually go before everything else, even old arctic armor applied before 'reduced damage taken'.

Of course, I consider it justified in light of possible exploits with low cost skills. However, I'd prefer lower values (something like -1 to -2) and having it apply before percentages, strictly as a mechanics purist, of course.

Ah I see, I had been counting the mana multipliers from support gems separately, but I see what you mean now. Thanks.