I think the main reason people are finding it hard to figure out how much to charge for MP3 files (variable? higher? lower?) is that they shouldn’t be charged for at all.
All such revenue is being extracted from the residual momentum of the copyright based business model as it slowly grinds to a halt – as that dwindling market of copy customers gradually realise how silly it is to pay for digital copies.
The pragmatic answer to pricing is that the price of MP3 files should gradually be reduced until it reaches zero or the purchase decision/hassle cost (thus maximising revenue extraction from a shrinking market). Unfortunately, those charging for MP3 files have an assumption that there is a sweet spot price that is non-zero.
The baby elephant in the room is the natural law that digital copies of published music shouldn’t and can’t be charged for – an elephant soon to reach adulthood. Ultimately, published music has to be free of charge – because it belongs to the public. Rather than the tragedy those brought up with copyright imagine this to be, it has its benefits to musicians in the digital domain. Freely copyable music provides free reproduction, free distribution, free promotion, and thus builds up the size of the paying audience.
“Eh? ‘Paying audience‘? I thought you said music had to be free?”
No, I said PUBLISHED music has to be free. After all, why should the public pay for what they already have? Such an unnatural notion only arises from the unnatural privilege of copyright.
A musician’s audience (their customers) pay the musician to produce music. After all, the musician is who they want to pay, and the music is what they want to pay for. The audience has no need to pay the musician (or their agents) for copies, given they have clearly demonstrated they can make those quite easily all by themselves1.
So, the musician’s new slogan is effectively “Get this one free, buy the next one”.
In more words: “The recordings currently freely downloadable from my website have been paid for by my keenest fans. I invite you to join them in commissioning future recordings.”
Don’t sell copies. Sell music. The market for copies has ended. The market for music continues unabated.
1 They can’t make vinyl pressings however, so there’s still a market for those, but the musician doesn’t warrant a cut (unless you still believe there’s a future for copyright).