According to reports, it appears that Apple is offering Apple Music subscribers a discount on the HomePod. Note that this seems to be a promotion currently running in the UK where Apple Music subscribers are receiving codes for discounts of £50 on the HomePod, bringing it down to a price of £269.
This is actually a pretty hefty discount when you realize that the HomePod in the UK is normally priced at £319. However like we said, this seems to be only a promotion being offered to customers in the UK and it is unclear if Apple has plans to eventually bring it to other countries, such as the US.
The codes are also valid for a very short period of time and apparently expire on the 16th of December, so this appears to be a rather short-lived promotion that you might want to check out ASAP if you are living in the UK.