My point is, most assassins have about 100 sp because of the FBH cards, if the backslide cost would become 40 sp, they can do it twice and then they'll have to berry to just move away.
This will affect their survivability quite fast and they'll find that out after going across the map 2-3 times already.
Champs will be less affected as their mana pool is a lot higher, perhaps the delay would be a better idea for that one.
Let me show you another point of view though.
If they escape to avoid combat, you're not in combat either, so it means you have time to change your tactics and move elsewhere.
If you're a wizard and your sinx opponent doesn't have a GTB and spams backslide after a few sonic blows, bother with setting random ice walls across the map and around every corridor, minimizing the play field.
This will affect snap as well as backslide, they can break the walls easily, but it slows them down greatly.
Anyway, this suggestion will need some more player input before it can be accepted or denied.
We want suggestions to be a bit more community based and also decided which ones will be used/declined.
Unbalanced ones can be reverted or adjusted.