If any of these companies is able to extract monopoly profits without fear of competition undercutting them or government/legal intervention, they will.
Right now all 3 are competing fiercely to win the hardware rental market, but this may not be the case in the future once the market matures, and they may raise prices to match leaving costs (as parent comment pointed out) if they can lock customers in.
The price must always go up over time. If there were a first rule of business, that would be that.
Price decrease is just a longer term strategy where it goes down before it goes up.
Hint: the cloud market has PLENTY of competition.