Anything based on the ARV is speculative until achieved. 

Only reason I can see is that you are speculating that even right now the over market price you are paying will still be a great deal when it continues to rocket up in value...and that value will be way higher than the market now.....that's speculation....not investing....

Some things you could to make your case is pull sale comps for the neighboring properties that sold in that range (simply being listed at $15-$20 psf doesnt count until a sale closes); you could also put together a pro-forma analysis for your speculative development using lease comps that justify a higher land price.

I speculate you aren't worried about Billions and anything under $1,000,000 to invest is pretty safe in real estate in most markets away from the coastal cities in my opinion.

If you're looking for potential future speculation, and willing to accept minimal cash flow or even a net loss on the rental, you might make out OK.

The next owner might see more value in the land in they can go either pure commercial or mixed use.But man I gotta tell you, this is a VERY speculative deal here with a ton of risk that you could get stuck with it.  

Not only does it not put food on the table, it IS arbitrary and speculative.

Approximately half of this is build to spec and the other half is speculation. 

If you buy hoping to make money through appreciation you are not investing you are speculating, and that is a much higher risk game. 8)

In the case that my Mother's neighbor sold their very similar home for a certain amount, you get an idea of what actually sells- not a speculation of the value based on statistics.With that said, comps can be emotion driven as buyers can fall in love and must have a property- potentially driving the price higher.