Going back to money and the "ethics" question, some more background information may be helpful for the discussion. The info quoted below must be basic common knowledge; it's in Wikipedia for example ("Construction of Gothic cathedrals"). The text refers to northern Europe, mainly France in fact, which was the cradle for this new kind of church buildings but it applies presumably also to Spain.
Motivation
The 11th to 13th century brought unprecedented population growth and prosperity to northern Europe, particularly to the large cities, and particularly to those cities on trading routes. The old Romanesque cathedrals were too small for the population, and city leaders [some cathedrals were built and financed by the townspeople themselves] wanted visible symbols of their new wealth and prestige. The frequent fires in old cathedrals were also a reason for constructing a new building, as with Chartres Cathedral, Rouen Cathedral, Bourges Cathedral, and numerous others.
Finance
Bishops, like Maurice de Sully of Notre-Dame de Paris, usually contributed a substantial sum. Wealthy parishioners were invited to give a percentage of their income or estate in exchange for the right to be buried under the floor of the cathedral. In 1263 Pope Urban IV offered papal indulgences, or the remission of the temporal effects of sin for one year, to wealthy donors who made large contributions. For less wealthy church members, contributions in kind, such as a few days' labour, the use of their oxen for transportation, or donations of materials were welcomed. The sacred relics of saints held by the cathedrals were displayed to attract pilgrims, who were also invited to make donations. Sometimes relics were taken in a procession to other towns to raise money.
The guilds of the various professions in the town, such as the bakers, fur merchants and drapers, frequently made donations, and in exchange small panels of the stained glass windows in the new cathedral windows illustrated their activities.
I think that reducing these complex interactions and motivations and religiosity - in a society of a distant past that was so different to our times - to simply "the church had too much money and should not have taken it from ordinary citizens" is an oversimplification.
Oversimplied one could also say: Those ordinary people used some of their income and savings to obtain spiritual benefits from giving money to have a cathedral erected in their town. Nowadays ordinary people use some of their income and savings to obtain spiritual benefits from giving money to be transported to Spain and walk a Camino.
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