In the case of people, they weren't being offered up as sacrifices (hopefully that's obvious), but offered as being committed to the Lord as she later did with Samuel. The values presupposed that sometimes people would make a vow and want to "take it back" or redeem it. Basically, they would, instead of giving up their child or giving their own life in service to God, pay some amount to get out of the vow. The reason for the differing amounts may have been based on the potential for service/work. Regardless of our current thoughts about equal pay for equal work, in the Israelites' time period, the amount of work which could be done by a man, given the physically-demanding nature of their lives, was greater than that of a woman. Notice that for those over sixty, the distinction between male and female was much less. Similarly, the amount assigned for children may have taken into account their current value of labor or the risk associated due to the hardships they lived under. The point is that these values do not indicate our relative value before God, but reflect the value of work that might be accomplished by each one during that time.
The more important concept is that God anticipated that they would make vows and later want to renege on them. And He provided a means for them to do so. Bear in mind that these vows were not required or mandated - they were simply times when people made a commitment to an offering of worship in the future, and then decided not to follow through.
The principle that God teaches us in this chapter, one that is very applicable to us today, is that we must not make commitments and then violate them without consequence. Whether it is a commitment to serve the Lord, or a commitment to your spouse, or a commitment to your children or your parents, as we read in James 5:12, "But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation."
YAY!! We made it through Leviticus!