How to format text field into currency (add dollar symbol, thousand separator and decimal value)

Default property:
ChangeNumberVar

OnChange property:
Set(ChangeNumberVar,
Text(
Value(Cost.Text),
“[$-en-GB]$#,###.00”
)
)

Language functions:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-language

You can watch the full video here:
https://youtu.be/StKOhfK2lt8