If you're getting grass-fed beef then the more fat the better ... there's good nutrients in grass-fed beef fat. Other than that, the difference is less between the muscle meats as steak vs ground beef, but there's a bigger difference between the muscle meats and the organ meats. If you want health benefits, see if your budget can support some liver or other organs regularly. Paul Jaminet recommends keeping liver to just 4oz per week, so a pound or two can last for a while.

Find a farmer near you who raises grass fed cattle. Ask for the cuts that are cheapest and/or no one else wants. E.g., shank, round, chuck roast, arm roast, heart, tongue, oxtail, etc. Any of these can make a really good stew with some vegetables, potatoes, spices, etc. Ground beef is also a good option, but I think a lot of the time these cuts are as cheap or cheaper and will give you some good variety.

Trader Joe's is now carrying grassfed beef from New Zealand in their freezer section for a reasonable price. I just saw it today for the first time. If you have a Trader Joe's nearby I'd check it out.

The biggest nutrient differences are going to be in the fat: higher omega-3, lower omega-6, beta-carotene, etc. Whole9 has a good buying guide for the Paleo poor, Mark's Daily Apple has covered things a couple times, Robb Wolf even has a video about Paleo on a Budget.

As far as meat is concerned, if you can afford grass-fed, go for the whole thing, fat and all. If you can't afford grass-fed, go for the leanest cuts (and grinds) you can find and then supplement with a healthy fat/oil (like coconut oil).

Costco usually has a good deal on a 3 lb. pack of "Organic Ground Beef" that someone on Paleohacks tracked down as being grass fed. Ground beef plus a basic spice rack yields endless possibilities from plain old hamburgers to Italian meatballs to Persian kofta kebobs to making your own sausage.

Do you have a local supplier of meat, or can you join a meat share? It can be cheaper than purchasing from any stores a lot of the time from what I've heard. If not, I'd say go with the ground beef myself. I pick up the grass fed ground beef from Whole Foods when I'm in Chicago only because I haven't gotten into a meat share or bought locally produced grass fed beef (yet! going to this year!).

I like the ground beef, mainly because I'm lazy, and it's easy to cook. I love steaks and all the rest, but I like my steaks cooked medium rare and I'd get upset if I overcooked it XD lol

I'm not sure about everyone else, but I think I might spend less now that I eat Paleo. Before I ate out a lot and now I'm forced to cook most/all of my meals. I can make bigger meals (like crock pot meals) and eat them for several meals.

Also, ground meat has endless possibilities: burgers, in omelets, taco salads, meatloaf, just a pile of meat...haha.

If you can find humanely raised ground pork I've found it tends to be about $1 cheaper per pound than beef, and if you mix it with ground beef it doesn't taste much different than all beef.

Grass-fed is nice and all, but not really a necessity. If you want to really find animals treated well, grass-fed or not, just buy from a local farmer. Local farmers aren't the ones running CAFO lots. Yes, the cattle may be grain supplemented, but that's not the end of the world. It's likely they're still antibiotic and hormone free, they may simply have a different fatty acid profile that grass-fed. Not that the fatty acid profiles are all that different between grain-fed and grass-fed. And when you buy something in between those extremes, the difference is even less pronounced.