Using LOBSTR does not add additional fees for the end user when submitting a transaction. The regular Stellar transaction fees still apply, however.
Stellar requires a small fee for all transactions to prevent ledger spam and prioritize transactions during surge pricing. All fees are paid in lumens (XLM).
The fee for a given transaction equals the number of operations in the transaction multiplied by the effective base fee for the given ledger (transaction fee = # of operations * effective base fee).
Effective base fee: the fee required per operation for a transaction to make it to the ledger. This cannot be lower than 100 stroops per operation (the network minimum).
Stroop: the smallest unit of a lumen, one ten-millionth of a lumen (0.0000001 XLM)
We (LOBSTR) set the maximum fee for 1 operation, which is 0.01 XLM so that your transaction certainly makes it to the ledger if the network traffic exceeds the ledger limit and the network enters into surge pricing mode.
Max fee for most transactions submitted from LOBSTR does not exceed 0.01 XLM. However, it can be as high as 0.81 XLM for certain transactions, for example when you are converting multiple pending payments on your account to AQUA.
That does not necessarily mean that you’ll pay the max amount. If network traffic is light and the number of submitted operations is below the network ledger limit, you will only pay the network minimum needed for your transaction to make it to the ledger.
Alternatively, when network traffic exceeds the ledger limit, the network enters into surge pricing mode, and your fee becomes a max bid. This amount can vary depending on network activity.
The lumens collected from transaction fees go into a locked account and are not given to or used by anyone.
Read more on Stellar fees here:
LOBSTR does not charge any fees when depositing or withdrawing assets through the deposit/withdrawal interface. However, asset issuers (anchors) may set their own fees for deposit and withdrawal operations with their tokens.