These are not fees for sacraments. These are called offerings, and they are governed by canon law (universal church law) and particular law (diocesan law). The Ordinary (bishop) does indeed establish the offering amount for the diocese, and typically stipulates how the offerings are to be used-- for example, in our diocese the offerings go into the works of charity account, not to the pastor. We use the works of charity fund to give to the poor and needy in our community.
This is the main canon governing the offering for sacraments:
Can.* 848 The minister is to seek nothing for the administration of the sacraments beyond the offerings defined by competent authority, always taking care that the needy are not deprived of the assistance of the sacraments because of poverty.
Please note the last sentence. Those who cannot pay the offering may still receive the sacrament.
I can suggest a couple of things.
First, since you have already talked to your priest, I would encourage you to remind him of the provision in canon 848 regarding inability to give an offering.
Secondly, I suggest you contact the cHancery office or office of judicial vicar or whoever is th head of finances at the diocese and get a copy of any diocesan synod documents or executive decrees from your bishop or other document that specifies these offering in your diocese and how they are to be administered. (ours is in the Finance Manual available online on our diocesan website)
Thirdly, begin to educate parishioners on the offeringm (this would be an excellent role for the members of parish council who are also likely unaware of how this all works), how it is used (often people think the priest is pocketing that money when in fact he is not), why it is asked for/collected, what it is and is not (a fee for a sacrament) and how to receive the sacraments when one cannot afford such an offering.
Fourthly, if you feel the offerings are truly “too high” then I suggest you contact the Diocesan Finance Council AND the Bishop and give them a well-reasoned explanation of your position and suggestions on what you believe the offering should be and why.