Train from Madrid to Granada

The price will not likely go down.

Notice that the earlier train departing @ 7:35am is a 'Promo' ticket (discounted) & it's price is €41,05pp.
'Promo' tickets sell out rather quickly!

There are a certain number of "promo" fares at different levels offered for sale for each train. When the cheapest are sold out, then the next level is offered, until no "promo" fares are left. So the price never goes down.

I have looked at that line several times recently and I suspect that there are no promo fares offered on that route except for the early morning train.

You could take the Alsa bus, and save some money. Note that the bus stations may not be as conveniently located as the train stations.

At less than €0.20 per kilometre surely a bargain.
The price will not reduce. Once promo prices are gone they are gone.

Great, thanks everyone! How early do we need to arrive to the train station before our departure?

About 30 minutes is more than enough. All Spanish trains have min security and access to the train platform is not permitted until 30 minutes prior to boarding. Ticket prices do not change like American airlines. Cheapest tickets will be the earliest. The standard fare never changes.

Do plan on getting to Madrid Atocha Station 20-30 minutes early. I found it very confusing to find where to go, and as said, once at the right place you have to go through security. Trains leave Atocha from two levels, so you have to go to the correct one.