It has been confirmed for the Wall of Spikes that you do NOT pay.
For wall of thorns with level 1 creature, I have no idea. My guess would be no.
Could anyone point out where it has been officially confirmed that Wall of Pikes does not make you pay to push through the "safe" way?
Wall of Thorns specifically says "a level 1 creature is not attacked" so it's not an "attack for 0 dice".
The reason I still want an offical ruling though is because although the wall doesn't attack it still is "a wall with the passage attacks trait" which is what force push is technically checking.