I’ll assume you’re in the US. If you aren’t, consult the laws/regulations for credit/debit card transactions in your country. If you’re in the US, there are statutes covering internet/mail order transactions and it can even vary from state to state, to a small degree.
It can be put through as a pending transaction on a credit card and depending on the issuing bank, they may hold the charge for up to a week or so. Most credit card issuers release the funds within 48 hours or less
If they don’t attempt the charge, the merchant has no way of knowing if the card holder has exceeded his credit limit.
However, the merchant is entirely within his rights to charge the full amount before an item ships. Many large merchants (not just tech companies) do this to protect themselves. You can read more about it here,
https://www.freeadvice.com/legal/putting-through-credit-card-charges-by-merchant-on-products-to-be-shipped/
If you used a debit card, laws may vary slightly from state to state, but generally are treated the same as credit cards.
If you still have questions or concerns I’d consult an attorney in your state. I don’t mean to sound preachy or condescending, but I’ve spent nearly 40 years in various forms of retail sales in several states and have tried to help customers understand the procedures and concepts of credit card transactions. I hope this helps.