Speed cameras are not toll booths. They do not take money from people indiscriminately but only from the ones that think that they can get away with speeding. (Unfortunately speeding seems almost necessary for e.g. delivery drivers which are in turn not the most well-paid jobs.)

Problem is rather how the fines are structured. 50€ might be a disaster for someone living on welfare while it's pocket change for others. If I remember correctly Finland countered this by making traffic fines daily rates of income.