Say you have $100. You pay $30 for gas, and have $70 left for other expenses. Let's say the oil cartel raises the price of gas to $40. You now have $60 left to pay for other things.
Because you now have less money, demand for other goods and services is lowered, and because of the Law of Supply & Demand, those other prices are forced down.
Now, suppose the government prints an extra $10, and gives it to you. Now you have $80 for other expenses. Your demand for other goods and services goes up, and so because of the Law of Supply & Demand, those other prices go up.
---
Another way to think about it. Money is affected by the Law of Supply & Demand just like everything else. Printing more money means there is more money (!), and more money chasing the same value of goods and services means the individual dollar are worth correspondingly less.
> So the government has boosted demand for groceries, thus causing them to be more expensive?
Increased demand results in price increases. The Law of Supply & Demand. Crazy, I know, but it is The Law.
> How did more money get into the hands of consumers aside from that one-time $1500 paycheck?
The deficit money got spent into the economy. It first flows into the hands of the voters being bought with it. Then, those people spend it, and it flows into the rest of the economy. It's like dumping a barrel of paint into a pond. It takes a while for it to spread out evenly.
Because you now have less money, demand for other goods and services is lowered, and because of the Law of Supply & Demand, those other prices are forced down.
Now, suppose the government prints an extra $10, and gives it to you. Now you have $80 for other expenses. Your demand for other goods and services goes up, and so because of the Law of Supply & Demand, those other prices go up.
---
Another way to think about it. Money is affected by the Law of Supply & Demand just like everything else. Printing more money means there is more money (!), and more money chasing the same value of goods and services means the individual dollar are worth correspondingly less.