Instead of paying 37 caps or more for Stimpaks, go to Tenpenny Tower. Go to the bar, save the game, hack the terminal, and activate the 50% VIP Discount and 10% Holiday Discount to get everything on the menu for what it is worth. The inventory is:

Beer: 2 caps
Stimpak: 25 caps
Vodka: 20 caps
Whiskey: 10 caps
Wine: 10 caps
After doing this, the value of items you sell there also increases. For example, a pack of cigarettes with a value of 10 caps now has a selling price of 9 caps.