In my current run, around 50 in my inventory in OWB (arrived there with 10), and another 130 in my oven at home in Goodsprings.
Never buy a single one, as I rarely use them. Currently I'm at 17 used Stimpacks in roughly 70hrs of gaming time, and at least 10 of them went on companions.
I cover my healings needs with Sarsaparillas, Water and Healing Powder.
High Survival Skill + Chemist = no need for Stims.
@ReallyDrunkHobo
Spent most of my chips for Doctors Bags there