Assuming the following conditions:

• Energy is not conserved - that is, you expend less energy traveling to the past than the net energy value of something you send to or bring from the past.

• It takes approximately 1 minute for the time machine to recharge and target a new time and location after use.

• The time machine can transport any object that can be contained in a space, but the space is fairly easy to expand. Think, “setting up a tent”.

All of this, I should emphasize, horribly breaks physics. But it’s not a stupid question. The answer is, essentially, “the economy, as we know it, collapses.”

A lot of people are going to point out that you can duplicate energy sources, items, etc… by bringing them from the past. Yes, that’s true. But what people are missing is that this enables exponential growth as well:

• I buy a gold coin. I put it in a large space.

• 2 minutes later, I set my time machine to go 1 minute back in time, collect the coin from myself, bring it to the present. Now I have 2 gold coins.

• 2 minutes later, I do this again - collecting the 2 gold coins and bringing them to the (new) present. Now I have 4 gold coins.

• An hour later of doing this, I have over 536 million gold coins.

This works for any reasonably sized object, by the way. A hamburger. A tank of oil. That sweet RTX 5090 for your new gaming rig. A nuclear warhead.

Society, as we know it, isn’t to survive this. The Earth probably isn’t going to survive this. The universe may very well not, although we’ve already broken so many laws of physics getting to this point that it’s a wash anyway.

tl;dr - time machines as popular culture imagines them are a cheat code.