Jakob, thanks for putting it so clearly and succinctly. I'd also like to suggest a "donation" option -- frankly I don't have a use for any of the paid features, for me T.O. is a staple but one I use for personal use. I'd gladly donate $5 to the project in exchange for absolutely nothing, if a method were provided.. but I'm still not clicking a "buy" button that doesn't tell me how much I'm committing to.

FYI: there are various providers, including Google, which offer APIs which convert prices between currencies on-the-fly using the current exchange rate. You could use one of them to display the price on the BUY button.

The problem isn't Chrome Sign-In, it's that your page has you explicitly click "purchase" in order to find out the price; that's a bridge too far for many people. It feels like poor form.

You go to the store to buy a new TV and find one you wish to purchase, but it has no price; you go to the clerk to ask how much it costs, and he says "you'll have to take out your wallet and start the purchase to find out, but don't worry -- we can cancel if you wish". That's where we are right now. Except there is no promise before the user clicks "Purchase" to even inform them that canceling is an option.