Out of interests how long did it take to put both those sets together? I can only imagine the bulk of them were sourced quite a while ago.
I think I got my first 30 back in 2002 which was a 30a Luke Bespin I think.
The last one was a 30b IG88 in 2010
I bought two separate large collections in 2004, plus convinced a contact I knew to part with two I needed, which gave me 22 plus about 10+ spares. That gave me all the first 10 on 30a and the next 10 on 30b.
I didn't bother with the first 10 on 30b except for the Luke and Leia because of the different card front. Which is why I had 22.
Can't remember when I decided to go officially for the first 10 on 30b but the 8 I needed did come fairly slowly. Really didn't believe I'd do it. Though in a rather geeky fashion I have actually got a record of when I picked them up.
I was trying to complete a Palitoy WBG run and managed to get the 30b in 2006 when a large collection came up for sale on Vectis. In 2007 I picked up a cheap 30b Lando that I thought I could sell on/trade. I'm guessing it may have been around then or early 2008 when I decided to try for the set. I already had 4/10!
There was a large Palitoy sale on eBay in 2008 and the guy had several 30 backs all of which were the 30b version. He had 4 I needed and I got all of them.
Got one the next year then the final one in 2010 to complete the run. In both cases it was through long term contacts I knew and so was in a good position to make a deal. Expensive though!
So that's basically how I did it. 4 separate large collections of 30 backs came up for sale plus 3 contacts were able to provide me the remaining.
My honest feeling is that is really the only way it can be done. Individual pieces rarely come up for sale on the open market anymore. When they did it was usually the basic common ones (Lando, HRS, Lobot)
The others only turned up when it was a large collection that someone decides to sell. They do happen. I think there's been 5 large collections of 30 backs come up for sale since 2004 that I know of. However it is worth noting that none of them individually were complete. And even if you put them all together you would only have got 1 complete set. Which probably gives you an idea of how difficult they are to come by. That's 5 people who tried and failed to complete which I imagine is why they decided to sell.
I'm not saying it's impossible but time and cost are going to be major factors. I paid a lot for mine and that was years ago. I remember paying around £500 for the Luke Bespin 30a. Back then that was a lot but there were many people going for them so competition was tough. But to see one on eBay go for 2k is scary. He's not that rare compared to most of the other 30 backs.