Let's imagine Mr. X is thinking to create a BitShares project and his future incomes will be coming from the referral fees.
He think about it, plan everything and when he is finally ready to start ... he sees that (after only one month) the fees are decreased by 25% ...
What do you think Mr. X will do ? Keep going on with his project ? NO ! That's too risky ! Maybe fees will decrease again and again and when he would have his project running, he would win anything. That's too much of a risk, why would he take it ?
Lower from 40 to 30 bts changes nothing for the perception of the fee price. On the other hand, it would have a disastrous effect on the incentive to build projects on BitShares.
One person who decide to wait or abandon his project is a lot of new potentials users lost !
I know with my team (BitShares French ConneXion) we are waiting to see what is going to happen before to start reaching people.
Let's think about it. If we had started with 50 bts / Tx we would be having these conversations about lowering it to 40. If we had starred with 30 bts / Tx we would be having these conversations about lowering it to 20. This is not a problem until we can prove its actually one.
If BTS would be valued at 2$ each, would a transaction fee of 0.045 bts be really different of a 0.06 one
The effect on changing it, IMHO, is 5% happy people and 95% bad stuff for BitShares future. Not because of the sum of bts paid for a Tx but because of the perception of BitShares as an unstable ground to build on.