When it comes to discussing the price and quality of a product, there are several synonyms to use instead of the word "costlier." Expensive and pricier are both common replacements, both indicating a relative increase in cost. On the other hand, premium suggests higher quality and, in turn, a higher price tag. Splurge, while not a direct synonym, implies that the cost is worth the indulgence. Similarly, luxury connotes a high-end product or experience. Lastly, upscale suggests something more high-end and exclusive, potentially leading to a higher price tag. When writing about pricing, there are several synonyms for the word "costlier" to convey meaning with nuance and precision.