FYI, I think your terminology is slightly non-standard though - (UK) english normally would describe any device worn on the head which allows you to listen to audio as either 'headphones' or 'earphones' interchangeably, with the distinction you refer to being indicated by using the modifier 'in-ear' beforehand...

Also the cost differential that you seem to suggest exists between them is not apparent - I have seen examples of both form factors of bluetooth headphones as cheap as GBP 10.00 (or less) at a minimum, and you could spend way over GBP 500.00 on either kind if you so desired - you get what you pay for, though...!