For Fusion, IIUC each of the parties individually had enough members (though maybe marginal), that’s why they could run candidates in the past. You need the members to be cashed up enough to be able to run a candidate though. So for senate, realistically you need 3, and that’s $6,000. If the party support is distributed around Australia, like Fusion’s is, you must run 3x a number of states, and that adds up fast.