My rule on what your store calls London Broil is to try to not grind it alone. I always save fat, and will grind in a little of the fatty part of the pork belly or use that saved fat (which I never have anymore, as butts are sold nowadays without a fat cap worth a snot). nothing wrong with a bit of pork fat in grind. The best fat to save is deckle fat from a brisket. Mixes with ANYTHING very well.
What I like to do personally is buy some extra fatty chucks on sale, and when I catch round (London Broil) for cheap, I grind a fatty chuck and a London Broil together 1-1 ratio. Me mixing and matching clearance meats is probably the main reason I grind 2x on my coarsest plate. I get a good mix that way.
The pretty half really likes almost fat free ground beef (sigh) for a lot of things. So I have been grinding some for her out of round. She hasn't quite figured out that my 85/15 is a bazillion times more tasty than her 97/3 or whatever she can find pre-ground, but we are getting there.
From your list, if you want to be economical, buy 10lbs of round and a 15lb brisket and mix it. Yeah, that's 25lbs of grind, but look at it this way - you would have grind for a long time.
Also - I have always found that brisket MUST be very cold to grind correctly. I can get away with fridge temp on just about everything else, but brisket grinds a whole heck of a lot better if it's semi-solid. The fat cap can be really soft, and soft fat is ok COLD. Not cold, it's a mushy nightmare. I suppose that is fat smear, which is a term I've only lately become familiar with.
I'm also a dirty glutton when it comes to clearance ribeyes. The ones that might be a tad too old to cook up rare/medium rare make the absolute best God's chosen grind. Fatty cheeseburger overindulgence. That's one time I'll gladly go over $5/lb for grind. So far, with all I had in the freezer from when I could get chucks for 3.99 and sirloin for 2.99 (and that's been at least 6 months), It's a good bet my price/lb on grind for the year is still still sub $4/lb - though the freezer, she has too many empty spots for my comfort. I bought 2 whole sirloins @ Publix a couple of weeks ago and I must admit, I cut some nice steaks, some nice steak tips, some nice stew beef and had mucho mucho left over for grind. And that was 4.99/lb - most I've paid for non-ribeye in a while.