I’m based in the UK. However, I noticed that the majority of prices I’ve looked at for WordPress themes or design work are based on the US dollar. So if I charged someone for doing them a WordPress theme, just for argument sakes, would it be acceptable to charge £1000 for example instead of $1000? Which currency should I trade in, US $ or GBP £?
If you’re charging people (worldwide), go with dollars, it’s the most universally accepted currency on the Internet, if you’re just serving people in the UK, go with pounds. In the example you gave it wouldn’t be acceptable to charge the same amount in dollars as in pounds, that’s called price hiking because their not of equal value, one dollar never equals one pound. If you want multiple currencies, you’ll need to have a script or manually take into account the exchange rate and add any applicable taxes like VAT if required for that country… it takes a bit of math but having USD, GBP and Euro is always a good plan - especially as most payment systems like PayPal (which let you accept payment) will convert the currency or allow custom currency payments online.