The P/S for the Rackbrute is missing; you'll find it under "Arturia" in the manufacturer list. And I don't think that Neutron belongs in there, since it already has a cab and power on its own. You want to use the not-exactly-cheap Eurorack cab space for things that DON'T have those. Or, a better way to put it:
Rackbrute 6 = $359 @ 171 hp (176 - 5 for the P/S). $359/171 = 2.10 (ish). This is the cost per hp of each space in the cab.
Neutron cost = $329. A Neutron takes up 80 hp, so $2.10 x 80 = $168. This is the cost to house the Neutron in the Rackbrute, which you would then add to the Neutron's cost, giving you an ACTUAL cost for the Neutron of $497.00.
Honestly, you would probably be better off if you used the space the Neutron's stealing for a basic voice AND a good sequencer AND some modules to screw with timing for the interface with the Minibrute AND the Neutron. The above might look convenient, but it's going to cost you some real $$$ in the long run.