How to get the Salvage Droid stages for the least bux?

I had about 650+ bux, but blew through them playing the Salvage Droid slots trying to get those stages. I think Kashyyyk was in the 2nd slot (at 15 bux a pop), and I must have wasted 345 bux but only have 2 wookies to show for it (not counting all the other crappy prizes).

I then used what remaining bux I had to rescan until Endor showed up in the 3rd slot (25 bux a pop), and I managed to get one of the Endor levels from there, along with 2 Ewoks and a rabbit-like creature.

I then saved my bux and had 75 when Endor showed up in the 3rd slot again. This time, in 3 spins, I got the remaining Endor level.

I'm still lacking the 2 Kashyyyk levels and the 2 Csilla levels, and since it's soooooo hard to get bux nowadays and so many places to spend it (dream jobbers holding out bux on you, and Decorator Droids not wanting to show up unless you bribe them), I would like to stretch my bux and know what's the most cost-efficient way to get those stages?

Also, does Kashyyyk still show up on your scans? Because I've only gotten Endor nowadays. I don't believe this is a limited event so I think Kashyyyk and Csilla should show up again, but they haven't for a while now and I'm getting a little worried.

So, for those who had gotten the Salvage Droid levels, how much bux did you spend (ballpark figure) to get them? What kind of Salvage Droid or which slot? Personally, I think spending bux anywhere but the last slot is a waste or maybe it was just dumb luck that i got those levels within a few spins...