Each B1 box costs 25 dollars, IIRC. A starter set costs 100 and comes with 2. You generally want 4+ B1s, so at least 2 core sets or 1 core set + 2 B1s packs are necessary.
The first option costs 200 dollars, but you can sell 1/3 of the first one (clone figs and cards) and 2/3 of the second (clone figs and cards, dice, rulers, generic cards, etc). That more or less will bring you back to 100 dollars.
The second option costs 150 dollars and you can sell 1/3 of the first one. That more or less will bring you back to 117 dollars.
It doesn't seem much, but if you end up wanting even more B1s (and using 6 of them is quite common), then we're speaking about:
- 3 core sets: 300 - 1/3 - 2/3 - 2/3 = 135 dollars spent (or close).
- 2 core sets + 2 B1 packs: 200 - 1/3 - 2/3 + 50 = 151 dollars spent.
- 1 core set + 4 B1 packs: 100 - 1/3 + 100 = 167 dollars spent.
Well, 135 to 167 is quite the difference - and you get 3 Droideka units and other 2 Grievous you can sell for collectors or just assemble in different ways. 3 Droideka boxes cost between 75 and 100 dollars. THAT money you'll be saving 100% for each new core set you get.