Yes, $900 is reasonable.
I was considering getting these complete setups (for the S30) , but in the end got the Ground Control coilovers from them and will get them installed locally.
They are really quite good with postage rates too. They charged me $169 for postage (for 4 coilovers, front LCAs and tension rods) and the box showed it actually cost $229 when it arrived .