A level 90 snake summon can 1-2 shot a team of 60k power opponents in GNW if used right.
I hope that answers your question.

Yeah it consumes both chakra and funds.
Level 89 to 90 costs 3850 chakra and 3850 funds.

Still worth it though for a capped summon.

And you need to feed it 700 chakra + funds every few days or it will go below 80% and stop giving the buff.