I was told, somehow mimicking reality, it is more expensive to survive in the core game after each new version. So in Sims 4, you either buy several expansions or it will be darn hard having your sims get out of the paycheck to paycheck zone.

Also the entry level stuff was harder to satisfy your sim in comparison (e.g. the entry level bed in Sims 4 recharged less the energy and comfort than in previous versions).

There was this comparison chart in some page but I can't find it, maybe it was a video..