All prices were sourced directly from the manufacturer’s website, and were accurate at the time of posting. I provided links to all the product pages, so you can easily double check this yourself. When the manufacturer did not provide prices in both €EUR and $USD currencies, I used www.xe.com to convert the currency and labelled all such conversions with “roughly …”
Of course there may be special offers from time to time, seasonal sales, group buys, cheap used copies for sale on KvR, and so on. But I don’t think there’s much point in listing sale prices in such a comparison, is there? You may be waiting forever for such a sale price to resurface, and may never get the same bargain again. So if you wanted to buy any of those products brand new today, the prices I listed are what you’re most likely to pay.