What am I missing? How does sp30 win any way you turn the coin?
Max profit for each of the 3 calculations is what?

Also, you are in fantasy land with 20% increase per month assumption.  You should use 35 as bare minimum and with next increases coming, it wouldn't surprise me to see a LARGE jump soon.

Why is this important? Because of salvage value.  How many people will want to buy your used s3 vs sp30?  You'll get a marginally higher resale price with s3, not sp30