Probably best to look up the local prices yourself? We don't know where you live.

There are fans that are cheaper that come close to noctua, but noctua are one of the best fans you can buy.

You're not going to find a significantly quieter 80mm fan. It needs to be bigger so the blade passing frequency is in a less noticeable range.

Well the cheapest crap fans are almost free, Noctua fans are certainly not free. So the added cost is the entire price of a Noctua fan.