Why, I have been playing for nearly four and a half years, I have all the GPD and very few normal habitats. If I want to buy premium habitats I do and I have only manage to finish in the top 2 about 4 times.
When I started playing the game was very Gold friendly, you earned gold 30 for installing a pop up game then another 14 for getting to a certain level and another 7 for reaching another level. We could quest for gold as well as getting it during the tournaments Rounds 15,20 and 25. GPD's went on sale for 400 gold.
Some players will speed breed to get a certain dragon when sometimes it just easier to buy it, the same applies for decor I suppose. We choose what we want to buy.