This market is designed as an experiment to see whether manifold odds will match the real stock market, or if it behaves more like a betting market. According to the 3 year gov bond rate, if you bought $412 worth of bonds right now, you would have $457 at this time in 3 years. Adjusted for the payouts you would recieve if you held spy, this difference results in the number in the title (436). Therefore, if people are able to hedge against the real stock market, the value of this market should start at about 50/50. However, it is very likely that this market resolves yes due to SPY's tendency to outpreform government bonds.
@KevinFischer I think interest rates have increased faster than expected. At the time though I was pretty confident in the math. Admittedly, I did not check options prices. If I do this again I will.
@KevinFischer Also, black swan risk has quite the effect on those tight spreads. There's a lot of people who will sell those spreads like you said, but a lot less people that will sell the 435 put. Think about how that spread costs up to $350 where as the $435 put seller is liable for up to $43k. People really don't like that kind of risk. "Picking up pennies in front of a steamroller" as people say, and you see that effect even here on manifold. Think about all those questions you've seen that are like a 1 in 10,000 chance closing in a few days trading at 99%