When purchasing or selling a Pass, a 0.06 TON transaction gas fee is charged upfront. Typically, this fee won't be fully utilized, resulting in partial usage. Consequently, any unused portion of the gas fee will be automatically refunded to you. For a detailed breakdown of the transaction, we suggest using Tonviewer.
TLDR: Today, every transaction costs around ~0.005 TON
Even if TON price increases 100 times, transactions will remain ultra-cheap; less than $0.01. Moreover, validators may lower this value if they see commissions have become expensive read why they're interested.
The current gas amount is written in the Network Config param 20.
For more details on Gas Transaction, please refer to TON docs