I'm sorry, my fault. I studied economics in Russia, and the term "dumping" was used in a more general sense as "selling goods or services below their cost".

Russian laws officially use the term "monopolistically low prices", and prohibit them if the entity engaging in such pricing holds a dominating presence in the market (and not necessarily for the goods that are being underpriced).

A correct term for the US is "predatory pricing", and it's also prohibited by the Sherman Act. For much the same reason, a large entity can destroy competition by accepting losses from selling goods below the cost. The border between loss leaders and predatory pricing is, as usual, very blurred.

If it's a large company, that can dominate the market by absorbing the losses until competition disappears?

Arguably, yes.

Forget about Costco, if some people here are so convinced this behavior is illegal they should be going after every fast food company that offers anything like "get a free/cheap xyz with any drink purchase!" Where the subsidy is obvious.

Costco gets to sidestep a lot of regulations because they technically are a private club with paid membership. The US anti-monopoly laws are also unusually weak.

In other countries, selling a $7 chicken if it's subsidized by the sale of other goods can indeed be illegal.

Tying is typically perfectly legal in both the EU and the US.

This isn’t even vaguely similar to illegal tying. The biggest problem being that the products almost certainly aren’t dissimilar enough to be considered “tied” at all.

So cable bundling channels is also “illegal” according to you? Since I don’t watch sports?

What are you talking about? Where is this illegal? It’s common to sell subscription services and then price them according to expected usage blended across the user base.

They give over 300k USD of free credits as part of the startup program without any commitment required...