2) If you expect software pricing to match the marginal cost to the supplier, then I think you're out of luck. All software is this way. There are huge up-front costs to build the software, and the cost of actually selling an individual license is close to zero.
Pricing in general shouldn't be about what a product costs to provide, but rather what it's worth to the customer.
However, I disagree with your first statement. Lets take Highrise pricing plan as an example. For the 6 user plan you pay $24/month - which comes down to $4 per user. For the 15 user plan you pay $49 - about $3.26 per user. So my total cost of course goes up with usage, but not in a linear fashion.
You could also make that happen with the $x/user/month scenario, but that gets probably rather complex without ending up with tiers again.