Bose soundsport audio only model. This model was on sale for £40 on prime day for amazon prime members only. This is the cheapest since then for both prime and non-prime. If you are a student you should get a 5% discount.
The sports edition is sweat and weather "resistant".
As far as audio quality, I feel this lacks a lot of bass, you can buy soundtrue ultra ear buds which will increase the bass but makes the earphones sound horrible so be aware.