How technology helps to sell good music

Every now and again Google Play gives some great discount.
It happened, for example, that Google Play store offered some really important classic album for only 99 cents as part of a weekly promotion.
This ultra-cheap pricing worked well on the 7th December 2014, when the store offered Pink Floyd's classic album, The Dark Side Of The Moon.
The album made a surprise return to the Billboard chart landing at No.13.
When released, the album held the No.1 spot in the US for only a week. It has continued to sporadically appear on the Billboard 200 since then, reaching 900 weeks on the chart in April 2015.