Transmuter can take artifact exp mats directly now.
The conversation rate is identical to a +4ed piece but no mora is required for direct material input. This represents a savings of 400-500k mora per patch compared to having to +4 stuff to feed.
Also if you're poor I'd recommend using existing +4 bricks as fodder for upgrading other artifacts instead of feeding into transmuter, to save a bit of mora. (~14k each)