Did a little informal research for your question:
The inertia system uses the body of the firearm as recoiling component, while the bolt and bolt body remains stationary, suitable for guns the use a heavy load. This system can apparently reach high rates of fire (5 rnds/sec).Used mostly in shotguns by Benelli.
The inertia-system is very simple, has less moving parts, and requires less cleaning than a gas-system. However, there's a little more free-recoil transmitted the shooter .IMHO, the inertia-system seems to have a higher efficiency than a gas-system.
Speed of the inertia-system
If recoil is a non-issue, the gas-system would be cheaper I think.
, but I hope that helps.