isn't Abalone one of the most expensive foods?

Yes, it's on the list of top expensive foods by itself (Brown-Lipped Abalone is the most expensive shellfish) and as an ingredient. Samundari Khazana curry contains Devon crab, white truffle, Beluga caviar, gold leaf, a Scottish lobster coated in gold, four abalones and four quail eggs.
The "Buddha Jumps Over the Wall" soup contains shark’s fin, abalone, Japanese flower mushroom, sea cucumber, dried scallops, chicken, huan ham, pork and ginseng.

anything less expensive that tastes like abalone?

It could be real cheap, if you swim out and pull an abalone off the rocks.