Are they worth it? Based on my calculations, it seems like it doesn't matter how many boosters you get (or even how often you win or lose), the number of games you need to play to break even is the same:

Assuming you win 1/3 of your games:
3 games cost 600-280 = 320, divide by 3 for ~100cr per game.
Earnings are 1+1+2 + 3B KR, divide by 3 for 1.33+B KR per game (where B is the number of boosters)
Breaking even at n games requires this equation:
1.33Kn - 100n = (1.33+B)Kn - 100n - 14000B
where B is number of boosters, K is crowns per KR, and assuming boosters are purchased with 200ce+100mist at 70cr/ce

Solving this equation for n yields n = 14000/K, so it would seem like the number of games to break even on ANY number of boosters is the same, and dependent only on the CE/cr exchange, and the cr/KR exchange. The interesting thing is the terms that are derived from how often you win also cancel out, meaning your win ratio has no effect on how many games you need to play (which makes sense if you stop and think about it: you are comparing against yourself). At the current exchanges (assuming a very generous 400cr/KR based on a 10KR enamorock retailing for 4000cr), it would take 35 games. If you allot 5min per game (also quite generous) then that comes to almost 3 hrs of straight game-time. (The generous allotment should basically cover the occasional bribe that nets you extra KR.)

So it would seem that unless you plan to play LD/BN for at least 3 full hours out of 24, getting boosters to farm for mod calibrators or enamorocks is almost certainly a waste of time, and it is less expensive to buy from the AH. The exception is obviously if you are farming for KR to buy recipes and bombheads, which cannot be bought from AH, in which case now you have to weigh how valuable your time is. However, the analysis does seem to indicate that if you do have time to burn, then you should get 6 boosters, since the number of games you need to play for break-even regardless of how many boosters is the same. Of course, this says nothing about the effect of flooding the market with enamorocks and mod calibrators, which will drop the cr/KR exchange.