The taupe grey one still includes mattress but is £10 more.
It doesn't seem to have mates included now?
Ikea cot beds are much smaller sizes, this is a full sized cot bed. It's also Obaby which is quite a reputable brand known for quality and durability. They have won quite a few awards, is 100% solid wood and comes with a 5 year guarantee. No comparison really.
Did you look at IKEA? I can see cheaper ones there including mattress and wondered why you thought this one was better?