I think you vastly underestimate how much demand is represented by 400,000 people willing to part with $1k before a product even exists. Refundable or not.
I am not questioning the demand. I am questioning the commitment of people who put down a refundable deposit on a product they had very little information about. I am one of those people who threw down my $1000 before any of the presentations. I am still not sure whether I will purchase one. My interest has actually waned with recent leaks like the complete lack of any dashboard readouts. However I am still perfectly fine with Tesla keeping my deposit until I make a final decision. The opportunity costs of that extra $50-$150 is worth a lot less to me than the chance of securing a Tesla quickly if a do make the purchase (not to mention it increases my odds of a full federal tax rebate). I can't imagine I am the only one of the 400,000 with that mindset.
You're not the only one. I'm nearly identical. Losing access to $1k for a year or two (with the ability to get it back within a few weeks) is completely a non-factor, and since it increases my chance of a $7500 rebate, seems like a pretty good investment, actually.
Also, same feeling of 'meh' based on leaks so far. I was really hoping for a scaled down S with fewer amenities, lower performance, etc. rather than something from scratch. The no dashboard instrument cluster thing bugs me, as does the fact that AWD won't be available initially (hurting the chances of the rebate if I want AWD), but I'll wait until at least the final reveal if not later to make my decision.