A new hair-growing drug is being sold for three times the price, per milligram, as the drug's maker charges for another product with the same active ingredient.
What is the meaning of this sentence:
This sentence does not clearly communicate the meaning due to the use of word "as". As we know, "as" can be used in different capacities. In this sentence, it may be used to communicate more than one meanings and none of these "meanings" make sense.
1: Express causality - Price of new drug is 3 times the price because drug maker charges for another product with same active ingredient. This is non-sensical since "price" in "3 times the price" is not defined. Secondly, the causal relationship is not logical. The price of new drug is xyz because the drug marker charges for some other product...
2: Express the idea of "while" - Price of new drug is 3 times the price while the drug maker charges for another product. This is also non-sensical since it implies that price of new drug is xyz and in the meantime the drug maker charges for another product with same active ingredient.
3: State a comparison - Price of new drug is 3 times the price. This is same as the price that drug maker charges for another product with same active ingredient. This is non-sensical since "price" is not defined. Also, the comparison is not correct.
Essentially, this question is one of those for which we need to select the correct answer choice such that it communicates a "meaningful meaning". Since "price" in 3 times the price needs to be defined, we need to use "that clause" to communicate the following meaning:
The sentence compares the price (using the expression - 3 times the price) of new drug with the price of drug that the drug maker charges for another product that uses the same active ingredient.
Shweta, I hope this answers your first question -
Does it not make sense to use "as" in the second clause?
Now for your second question, answer is
yes.
Comparative words such as more, less, greater, smaller, etc. should be followed by than. This idiomatic usage is frequently tested on GMAT. For example, more...compared to is incorrect.
Please let me know if you have any further questions about the above.
For e-GMAT users, such
comparison idiomatic usage is explained in the concept file Idioms - Comparison.