On the Strip is tourist trap stuff. If you can get away from the strip (rental car, or public transportation is required as none are in easy walking distance of the Strip.)
A few good and inexpensive buffets: (all well under $20)
The Orleans west of the strip on Tropicana has a very good and inexpensive buffet. (Best use a rental car to get there.)
Palace Station, north of the Strip in the "Downtown" area on Las Vegas Blvd. (catch the bus at the strip north and you'll go by it a little north of the Stratosphere, or drive north on Las Vegas Blvd. from the strip)
Boulder Station, on Boulder highway at Lamb/Desert Inn. (From the Strip, go north on either I-15 or Las Vegas Blvd. to I-515 and take I-515 north to Boulder Highway exit 70 and left on Boulder Highway.) It's a good place to eat when returning from a drive to Lake Mead and Boulder Dam It is just off of I-515, which is also marked as US 93/95. (I-515 to exit 70 and right on Boulder Highway)
My favorite is the Cannery. (There are 2, but I've never tried the newer one as I live close to the older one. ) The older one is on Craig Rd, west of I-15. (I-15 north to exit 48, Craig Rd. Left, over the interstate and it's on the left a few blocks down.) Its buffet is almost identical to the Orleans and further away from the Strip, but it is a great place to eat on your return from the Nascar track or if you have driven north of Vegas to see places like Valley of Fire.