TL;DR It’s very cheap; actual prices for hauling depend on many factors not considered in the proposal.
Your example has a very good reward—for a standard, casual delivery between Highsec hubs. However, you may want to tick the “rushed” box (~70m with Red Frog, ~50m with PushX, ~30m public with Haulers Channel). Then the Red Frog rate would indeed roughly match your proposed 0.5% per jump for 1.5b value (and up to 875k m³ volume)—in this special case.
With lower values, higher volumes, or in Low/Null, the proposed prices would quickly become way too low compared to actual prices. E.g. a 350m value delivery from Jita to Amarr would cost ~15m according to your proposal (that’s ~20% of the Red Frog rate), and since the proposal is not region- or security-level-restricted, or takes other factors into account, you’d pay the same rate for delivery from Outer Ring to Curse (or ~75m vs. 650m with Black Frog). That’s just not considerate enough.
Of course, if your proposed mechanic spawned public courier contracts, I’d be all for it (more content \o/), but they would have to be competitive. Automatic spawning of public courier contracts is a topic of its own, though, and you already mentioned that players (and by extension also any NPC convoys) would be too slow to make sense for your proposal (e.g. a DST, not even a slow freighter, needs approx. 15 minutes for a rush between Jita and Amarr, gate-to-gate).
You will need to come up with a more detailed pricing scheme as a basis for this particular part of the proposal to avoid punishing the hauling profession too much. Consider ISK/jump, time to complete, security levels, volume, value, system activity, as well as the type of ship needed (including it’s align time, warp speed, and PvP capabilities).
Alternatively, base your proposal on going Jump Freighter rates (ISK/m³/ly), considering fuel cost, pilot skills and fitting (at 1.500 ISK/unit of fuel roughly anything between 10 and 70 ISK/m³/ly, and that’s only the actual cost of moving a fully loaded JF through 1 cyno, not including time spent, risk taken, number of players involved, or anything else). Delivery with a JF would be reasonably fast and secure, though, and probably matches your proposal best (if they could jump directly to Highsec—but then that would be another highly superior feature of your proposal compared to what haulers can offer).
If this were actually to be implemented, I’d probably be part of a protest somewhere, mass self-destructing a bunch of Freighters 
Some calculators for reference: Haulers Channel, PushX, Red Frog, Black Frog.