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While it varies, a general egg donation might harvest ten eggs from the woman. The success rate for fertilization is around 75%. While the embryos can be frozen rather than destroyed, chances are many of these embryos will never be implanted, and not many people will want to keep paying the ~$50 a month per embryo to store them indefinitely, but it isn't known how long they stay viable for. If the parents stop paying, then the embryos are thawed and tossed. That is something to think about from the perspective of life, especially when other alternatives (like adoption, or getting a frozen embryo from a donation center) are available. A genetically distinct, developing human organism begins at conception - so we should be careful when deciding to create life knowing it will probably be destroyed.