Because 360 gold for a temporary buff IS expensive.
How about 72 gold is that expansive?
That's the price Auntie Ethel sells them for to a 16 charisma character. Even if you started the trade with a 10 charisma character it would only cost 90 gold.
Personally I am not bothered one way or another about their duration. I just want you to stop making things up to support your argument. Merchants do not sell an Elixir of Hill Giant Strength for 360 Gold.
