You can get HoT and/or PoF for 50% cheaper until june 27th from official Guild Wars 2 site
This means you can get both expansions for 25$/€ total!! Or just PoF for 15 $/€, not sure how you add only Heart of Thorns.
Makes me wonder what was the point of earlier 30% sale but guess they still riding the hype train from Bless.
The basegame is free but theres pretty harsh limitations for f2p players, so you dont need to spend any money on it, just get the expansions and youre good to go!