If you live in the US the robos cost close to $20 each, if you adopt animals from SPCA or Pet-Co has adoption animals they ask a $5/animal donation fee. So that could save you $30 & you might be able to give needy hamsters a good life they otherwise wouldn't get to experience.
I was just posting on another thread that adoptapet.com also may have hamsters up for adoption in the US, it's based on zip code locations.
I'm sure you know that if you plan to house them together they need suitable housing, larger tanks or cages.
Edit: I just saw how you have 720 Sq in cage if you go with 40x18 in
You would need an extra cage as pairs often need splitting up. Have to prepare for this immediately as fights can happen in middle of night & lead to serious injuries or death.
It's not recommended to get a pair of robos as you would need to watch them closely & it can be stressful if they start fighting (as a first time hamster owner). There is a vet fund that you would need to consider with any pet but pairs may be of an increased risk for a vet.
If you really have your heart set on it you could try to adopt a bonded pair already through the rescues I mentioned & of course there are others as well.
But you would need 2 of everything in the cage to prevent fights. Territorial fights. If your buying from a large chain pet store be aware that robos in the same cage on the floor doesn't mean they are from the same litter as they come from farms. Litter mates have the highest chances of not fighting so definitely try to find a bonded pair or litter mates if trying to have a pair
Hope all works out!