Well, here's a few hints.
First, your price per unit is a good thing to know. Right now, you're paying $5 per unit.
When you sell one unit, you make $5. When you sell a two-pack, you still only make $5. And when you sell a three pack, you're again making $5. You should calculate this by subtracting the unit price multiplied by the number of units sold from the sale price.
Now, let's look at your oppurtunity cost. If you sell each unit individually, for $10, you will make $560. Subtracting the cost of goods sold, you end up with a $280 profit. Here your profit margin is 100%, meaning for every five dollars of merchandise you sell, you pocket ten dollars.
But, if you sell everything as a a two-pack, you're only getting half of that profit- $140. Your profit margin essentially gets cut in half when you sell two-packs.
By the three pack, you're only making 2/3rds the profit of selling single grams. Around $90. This sucks.
Throughput is always good- meaning, as your sales volume increases, your profit over time increases. If you sell 10 single units each day, you've made $100, and half of that is profit. Sure, you may have to re-up more often, but you'll be making more cash.
You might want to consider reinvesting some of your earnings. Generally, the economy of scale can be utilized to your advantage, and most sellers offer substantial price breaks when you buy 112 "units"

This way, you can lower your price-per-unit, and increase your profit margin.
Other suggestions:
Brand your product better. Use interesting bags with nice designs. As a side note: smaller bags make smaller portions seem larger.
Sell your product in an area with limited supply. The demand for units is relatively price inelastic- especially in areas where few alternatives exist. For example, in my country, persons under the age of 21 are not allowed to purchase or possess alcohol. This means that other alternative intoxicants are in higher demand among those whose access to alcohol is limited. Likewise, avoid areas with cheap and readily available alternatives.
Change your portions to better capitalize on existing markets. Sell half units for $5, full units for $10, one and a half units for $15, and two units for $20. These portions better preserve your profit margin.
Increase your market share by hiring other people to sell some units for you. They can retain a certain percentage of the profit. You can maximize your profit by having them sell in areas where you don't currently have market presence, as their sales (which you will not make as much money off of) won't be made to your existing customer base.