Spot prices fluctuate based on demand. Apparently there was a huge demand for g4ad.xlarge in Ohio which pushed up the prices. Interestingly g4ad.2xlarge is now cheaper on Spot than g4ad.xlarge which is interesting.

Also check out other regions - many have g4ad.xlarge available at a lower price than Ohio. The Spot prices are dynamic, the rock bottom is 70% of the on-demand price but when the demand is high the price may increase above that.

I suggest that you leave it to the template to figure out the best value for money, that's what the InstanceFilter lambda is for.