I think unless they are very new to the online game, it should be very clear to a free player that other players have exapansions because they paid for them, and they have that option themselves. It's another questions if the Store tab is easy to find.
The price increase is AFAIK based on
1) the fact that the Gold subscription now includes Renaissance (it does so since roughly a year, so that may be the reason only if you did buy a year ago for one year, without Renaissance), and/or
2) the exchange course of your currency to the Euro has changed since the last year.