the aws smallest instance comes at 450$/mo (about 300/mo paid upfront), the one he suggest comes at 200$/mo but the gpu seems cheaper. still one would need some sort of payout to keep it running, it's not exactly cheap and you need to shell 2k upfront
But they could terminate your instance at any time...
Usually, training step is the one that takes the longest and that can take a whole day. Evaluation step can be done on CPU usually almost instantly. Not sure what the utility of spot instances is in deep learning. Not to mention code complexity and Dev-Ops investments to run on very transient hardware.
Finally, you can't haggle with AWS, but you can basically name your price with private dedicated server providers like that.
the net comes pretrained. I haven't dug into the code much, but from the surface it seems it works by using the net as a scoring system for feature similarity, and then does a gradient descent on that (in very broad terms, I saw the style layer being used multiple times at multiple scales, probably to capture high and level patterns independently)