You will always find people who spent money on literally anything so you may have chance to capture a niche for yourself. As for Spotify yes i have seen plenty of people buying it as it is one of the best cloud song streaming out there but i think they should change pricing for time being to attract more subscriber as pricing can be its weak side. So if you can find a lobby or create audience in social media who are looking for cheap solution then you will do good.
Usually there is not only spotify for cloud song streaming but also there are a number of other platforms which also now includes youtube music. These kind of platforms have some subscription fees which is even been compensated to the origin of the music series. These kinds of premium platforms were not in that demand few years ago but now, with the increasing demand for the entertainment industry, I have also seen a lot of people buying premium memberships just to stay updated to the firms.
In case of bitcoins, people like to spend their coins in buying such memberships or goods and services and hence a number of people might buy membership from OP if he is selling the same membership for a cheaper price.