First, yes, in my opinion it's worth the $50M+. According to todays AMA, it took them at least 3 years to get 100k users. It took them 6 weeks to reach 200k. It's taking them 2 weeks to reach 300k. In other words, it's growing very, very quickly. The valuation will continue to grow with it.
Which leads into whether it will sustainably grow over time. They continue to add utility to the SPS token. It will soon be able to be used to purchase in game assets and potentially be burned. It will be able to be used to stake on individual players. And, right now it can be staked to earn more SPS.
I am currently holding it and staking everything daily. I'm just doing it right in the game as one, it's the easiest, and two, it's currently paying 280%.
At these prices, I'm very confident it will hold its value and I actually expect it to rise pretty significantly. I would not be surprised to see it climb well over $1. Earning 200%+ with a reasonable expectation of price improvement? Yes, please!