However, what is lower transaction fee? I don't understand that part. As I know, exchanges or Peer-to-peer exchanges will charge you fix trading fee which is in percent of your trade value. Your trade partners no matter they are newbies, VIP or trusted ones, don't affect transaction fee or trading fees of your trades with them.
When you gain the trust of a party you eliminate the need to pay third party fees and when you do more transactions with the same person the fees will be lower instead of trying to find a new trusted member.
For example, when you deal with a legendary member with moderate trust, you will initially need to use the guarantee (additional fees) and then they can make weekly transfers of medium amounts without being afraid of fraud.
In addition, for example, in my country, when you receive a transfer from an unknown person and then receive a fixed amount of transfers every period, the bank rarely considers this activity suspicious, but when you make several transfers with unknown persons and from multiple countries, the account will be frozen and you will be asked for more fees to verify transactions.