Interview we Harada

There is also the problem that even if a collaboration moves forward, Tekken most definitely has the highest cost of development for one character in the genre (someone with development experience will recognize this right away because of the complexity in the rigging of the character models, the volume of animation data and scripting needed, since each character has several times the moves of other fighting game characters). This is true for existing characters, but even more so for collaboration characters since everything needs to be made from zero, thus increasing the cost even more. So, in that meaning, yes, it is more difficult.

Source - http://tekkengamer.com/2018/05/23/harada-san-says-its-safe-to-expect-more-for-tekken-7/