Well, as it currently is, all summons can be made for free. It’s just a matter of getting free tokens, coins, and keys. It only becomes a paywall if players decided to buy gems just for them to summon more to have more chances getting the hero, and most players, not having the same luxury of being able to buy, or willing to buy, the gems required for summoning until the hero chased or sought after is obtained.
But that boat has long sailed. New heroes being developed for, and added to the pool of heroes in, Season 1 is very very very very very slim. We are currently on the 4th season. If SG is constantly creating new heroes, they may be designed as future HOTMs, or event heroes, or season/al heroes. The only instances where a new hero is developed for an event that was already concluded is Ursena for Season 2, and recently (I hear, sorry, I am not in beta) Salmon Loki for Season 3. Also the likes of Krampus, Vanda, Francine, Finley, Black Knight, Lady of the Lake, Snow White, Jabberwock, Marie Therese, Killhare, Sir Roostley, and a bunch more 3-5* heroes from those respective event portals.