Las Vegas has dozens of great buffets and hundreds of exceptional restaurants. However given the cost of most of the Buffets - $20+, with the best restaurants much higher than that, and given the tendency to have great food at many conference venues, the budget approach is to do a lot of great eating at the parties and events that tend to go with conferences and tend to have exceptionally good catered food and free drinks.
However here's an excellent list of ten Las Vegas Buffets with prices:
Not on the list is Terribles Buffet about a mile off the strip on Paradise. Popular with locals I found it to be OK but not exceptional. The 9.99 price was very reasonable, but I think for the cheaper buffets Excalibur is probably your best choice.