If only you had known about diskprices.com you could've saved yourself the trouble.
I am planning to add some aggregated statistics (e.g. price trends by brand/category)
Are platforms like Keepa violating Amazon's ToS then?
I also played a bit with scraping, and you can do that quite easily, but if you want to do it at some scale, you need lots of proxies, and quite soon it gets slow and overkill