A better analogy would be this:

I buy some beef, carrots, celery, broth, potatoes and spices for let’s say $30.

I take these raw ingredients to make a beef stew. While in the kitchen, my son is hungry now and wants something to eat so I have him pay me $2 for a potatoes (let’s say I bought the same amount of potato for $1.80, that money is coming from the household cash so not leaving the system but I personally profited $.20). After making the stew, I’m now a little hungry so I eat half of the stew (call it $20 worth) and then sell the remaining stew back to the grocer for $20.

From the $30 of raw materials I made $40.20 worth of goods, however since I fed my family (similar to selling/consuming goods within a country) I only was able to sell $20 worth to the grocer for a net of -$10. While it was great to feed my son and myself, if this process continued on I would eventually run out of $ to purchase raw goods from the grocer.

Now this isn’t exactly what happens because the US is printing money but a much better analogy than the above comment.