Is abalone high in cholesterol?

Same as most animals. The cholesterol content in most animals per unit weight is quite similar. The difference is usually related to their relative content of saturated (like marbled fat in red meat) and polyunsaturated (like omega-3 fats in sea food) that determine their health risks. Abalone likely is very low in saturated fat itself, but like most sea food, gets less healthy with the drawn butter that accompanies it.
LDL, not Cholesterol. Cholesterol is a fat molecule manufactured by every animal cell, a building block of each cell membrane (enables membrane fluidity/movement without tearing), is fundamental to the survival of every animal cell. Lipoproteins (proteins which transport all fats in the water outside cells) is the correct issue for artery disease (e.g. Ldl ?700 nmol/l, HDL ?45 µmol/l). Cholesterol ?$, but misleading.