With a 50/50 win ratio, you average 25 gold a game (20 lose, 30 for a win, (20+30)/2 = 25). 150% of 25 is 37.5. You're getting 37.5 gold extra per game thanks to the stim pack, for a total of 62.5g on average per game, but we're only looking at the 37.5 gold. $9.99 on the shop can buy you a 10,000g hero. This is our standard for comparison because they are the same price. To get to 10,000g using the stim pack, you need 10,000/37.5, which is 267 games to equate to 10,000g from stim packs alone. Over a 30 day period, that's 8.9 games a day (267/30). At a 25 minute average match length, that's 25*267, you're looking at 6675 minutes of pure match gameplay, or about 111 hours or pure match gameplay a month. That's 3.7 hours a day over 30 days to make the stim pack even break even.