So are they stealing from their employers or is something else going on?

nope - a.i companies to promote their platforms offer 'a.i' credits to startups usually worth 10ks, 100ks worth of credits in $ terms.

so to a startup - you can trade your credits - then get actual cash.

just like you would if trading debt etc.

What is the logic behind selling at such a steep discount? Lack of buyers or trust? Seems insane to sell tham at -50% or more, especially since you can use them yourself (if you're a startup)

Risk-reward calculus. A buyer may not take the risk or hassle of going underground only for a small upside. Basically it is not as tempting at 90% of list price, but it is at 10% .

Stolen credit cards

Demo accounts

Free trials

Unlimited chat relays (eg chatgpt chat)

Leaked company credentials

Etc

And I’m pretty sure that’s just the tip of the iceberg.