It is not possible to pay the additional cost in situations where Hashmal is cast without paying any cost in the first place, due to an effect of some kind
In these past showcase cards, the metal Viking treatment was only applied to legendary creatures, one legendary artifact and one very special enchantment: The Prismatic Bridge
All you need to do is flood your board with plenty of creatures with one toughness, and suddenly you can pay one mana to draw two cards as often as you want
If you have more money than time, or just some budget allocated for MTGA, this route might be the best bang for your buck
These cards not only offer unique strategies for seasoned players but also open doors for newcomers to explore White in ways previously deemed unattainable
It gives you the opportunity to take control of a situation, but at a cost that benefits your opponents