Interesting numbers. Let's try a variant case. Suppose in addition:
You're assuming that the non-reusable launch vehicle cost per launch is $60M. OK, let's start out by assuming 1/3 of that is fixed costs and operations costs, and 2/3 the vehicle cost, which is split evenly between the two stages (first stage is larger, but not proportionately more expensive). So, of the $60 million, $40 million is spent even if the vehicle first stage was free.
Now assume that re-usability increases the launch cost by, say, $5 million (launch operations are expensive! and the cost is not entirely the vehicle).
Assume that all the stuff needed to make the first stage reusable increases the stage cost by 25%, from $20M to $25M.
And assume that the delta-V and the added mass to do the fly-back decreases payload by 10%, and that the price you sell the launch for decreases a similar percentage (some payloads won't care, but some will.)
First off, the current cost of the rocket already includes the costs to do reusibilty, so the cost of the first stage will not increase- it is designed be reused up to 10 times right now with no change in hardware.
Secondly, the cost of the 2 stages are not even remotely close to equal; the first stage has 9 Merlin engines, the second stage only has 1. An estimate of 6 to 1 (first to second) for costs would be more reasonable.
Thirdly, the payloads currently quoted already include reusability (16MT to LEO and 4.5MT to GTO). No loss of earnings there.
So none your variant assumptions are useful for this discussion.
Let's look at some other factors you haven't considered.
Like the space shuttle, SpaceX now has a rocket for examination that has flown a full mission and hasn't had a 6G salt water landing. This means that they will be able to do full engineering analysis on what stresses the rocket actually experienced during a flight event that increase all steps necessary for re-use. The results of that analysis will allow them to determine what parts of the rocket need to be enhanced or reduced to meet the 10 tens re-use goal. SpaceX has the luxury of being to make changes to their rocket without Congressional approval, so this information can be used immediately to improve the vehicle. The design goal of the Falcon is that the rocket need not be "refurbished" after every flight, just put through some standard flight maintenance tests. Having the flown stages available for analysis will help them to meet this goal.
Additionally, SpaceX currently has launch costs based on 6 launches a year. As they have already demonstrated the ability to launch with a cadence of 2 weeks several times, being able to increase their launch rate to a minimum of 1 a month will cut their overall costs per launch.
Let's assume that a slight redesign based on analysis of real-world data let's them increase reliability of the Falcon 9 to 1 in 100 and increase the payload by 1MT to GTO. At 5.5MT to GTO, this let's them handle 90% of all GTO launches (6MT is at the current top end for commercial satellites to GeoSynchronous orbits) with the reuable design. 5MT is compable to $137M Ariane 5 capbility or $132M for an Atlas 5 launch for NASA with both the throw weight and reliability requirements necessary to get these flights.
$60M to launch the current, reusable Falcon 9 1.1FT.
33% is launch cost. - $20M
56% is first stage - $34M
11% is the second stage $6M
Assumption 1: increase in flight rate reduces launch costs by 25%
Assumption 2: landing/recovery/flight readiness check costs $5M a launch
Assumption 3: 10 flights reuse of the first stage = $3.5M a launch
Under these assumptions:
Launch cost $15M
First stage $3.5M
Second Stage: $6M
I'm OK with those numbers given what they can charge and how quickly they can do regular launches. Where they will really rake in the cash is for a Facon Heavy launch (same vehicle with 3 first stages instead of 1) with 56MT to LEO for an asking price of $110M and a cost, by these assumptions of $35M. They could even reduce their price after a few launches of the Heavy to $56M, and start launching bulk cargo to space at a rate of $1000/Kg