some carnicerias have some of the best tacos cheap but I think a lot of them weren't doing sit down with covid.
Pretty much anything outside the casinos is going to be less expensive by a good margin.
You could probably spend an entire trip just eating from places in chinatown. Saporro revolving sushi is pretty good. Lotus of Siam was always a favorite for thai, haven't been since they moved to a nicer location.
The casinos off the strip often times have good deals on prime rib and buffets. Bareleys brew pub and casino on sunset was one i usually enjoyed for inexpensive beer and prime rib. Great sushi place by there with all you can eat called bluefin.
Couple places like town square and the district in green valley have slightly upscale food that is still a good bit less than some of the strip stuff.
There is really a ton of stuff, just search what the group is interested in and check out some reviews for places not right on the strip.
You also have to factor in the convenience though. If you have a larger group and everyone is trying to uber or something you have to be mindful of those costs. If you really want to get away a little cheaper buy some stuff for breakfasts and lunches at the grocery store and you can do fairly simple stuff like grabbing pizza and wings or whatever.
The whole having some stuff for breakfast and lunch can't be overstated though. You could get a $7 coffee plus some $4 pastry for breakfast and a $15 sandwich plus $3 coke and $2 bag of chips for lunch and still end up spending $40-$300 a head for dinner.
or spend like $5 for shit for breakfast and lunch and not be bothered as much spending on a nicer dinner