Most developer tools bill in USD. If your revenue is in AUD, every invoice carries currency risk and a conversion spread, typically two to three percent on a standard business card, sometimes more.
Two or three percent on a small hosting bill is nothing. On a meaningful infrastructure spend it's a real number, and it moves without warning when the exchange rate does. Budgeting in AUD against USD-denominated costs means your infrastructure line item varies by ten or fifteen percent year to year for reasons entirely unrelated to your usage.
There are also accounting consequences. An AUD invoice from an Australian entity comes with GST handled the way your accountant expects. A USD invoice from an overseas supplier is a different treatment, and reverse-charge GST on imported services is a conversation worth having once rather than discovering at tax time.
Where local vendors exist and are competitive, SMS is the clearest example, billing in AUD from an Australian entity is worth more than the headline price difference suggests.
Where they don't, the mitigations are ordinary: a card with low foreign transaction fees, or a multi-currency account holding USD if your spend justifies it.
Our category pages record billing currency and entity per vendor so you can filter on it rather than discovering it at checkout.