**Core Concept**
Liposomal amphotericin B is a formulation of the antifungal medication amphotericin B, which is encapsulated in liposomes to reduce its toxicity and improve its therapeutic index. This formulation is designed to minimize the adverse effects associated with conventional amphotericin B, particularly nephrotoxicity.

**Why the Correct Answer is Right**
The correct answer is A. Lesser nephrotoxicity. Liposomal amphotericin B has a reduced nephrotoxicity profile compared to conventional amphotericin B due to its liposomal formulation, which limits the distribution of the medication to the kidneys and reduces the risk of renal damage. This is achieved through the encapsulation of amphotericin B in liposomes, which slowly release the medication and reduce its accumulation in the kidneys.

**Option A:** is incorrect because it's the correct answer.
**Option B:** is incorrect because liposomal amphotericin B is generally more expensive than conventional amphotericin B due to the complex formulation process.
**Option C:** is incorrect because infusional toxicity is still a concern with liposomal amphotericin B, although it may be reduced compared to conventional amphotericin B.
**Option D:** is incorrect because the administration frequency of liposomal amphotericin B is typically daily, not once a week.

**Clinical Pearl / High-Yield Fact**
Liposomal amphotericin B is a good choice for patients with severe fungal infections who require a broad-spectrum antifungal agent, but it's essential to monitor renal function closely due to the risk of nephrotoxicity.

**✓ Correct Answer: A. Lesser nephrotoxicity**