No. Both are in DS. Sustenance is far more expensive, however. Look here - I even created a thread about sustenance items last year.
I was thinking about this the other day and how to present such a situation to the PCs. Here is a vignette.
“How long has it been now?”, one onlooker asked another.
The psion had been sitting there for 40 days already. The psion wanted to prove that through psionic control, one could go without food, water or shelter indefinitely and was planning to do so for 100 days.
“Day 40”, replied the other onlooker. “Can’t tell if he is thinner than before. He was already skin and bones. A lot darker though”, the other onlooker added.
4 days later the fasting psion was found dead, a crossed legged corpse in mediation position. There were disputes among the city folk about how it happened. Some said that there were limitations to even psionic powers. Others said that the psion was old any would have passed on anyway. Some thought it was murder, by poison perhaps. Almost all of the city folk agreed that it is best not to push your luck and not eat and drink at all.