It really depend on what kind of ASIC you need! However, a 400k gate count doesn't looks like simple one.
For little quantity , go to find some FPGA from A@l?t*e@r?a , Xilinx, ... It will cost US$50-100 each. Or you can go for mask version of FPGA from the company above, but that chip only good for general purpose (high power consumption, noise, ....).
If your require more than few hundred, I suggest you can go to find a design house. The implement cost from US$50K-200K depends on your design. Then each chip will cost US$1-2 only .
Usually, if a ASIC with 400k gate. I suggest you go to for a design house for implement and production. That is easy and time save.