A woman seeking pregnancy is in a position of a very hungry person in a grocery store. This sometimes can cloud her rational judgment in making a very important decision on how many embryos to transfer. 

Transferring more than one embryo will always increase the chance of pregnancy in this transfer. It may save money because fewer transfers will be required to become pregnant. But, can this justify the risk of potentially enormous and life-long consequences, both, emotional, physical, and financial, including the cost, of premature birth?   

Important to keep in mind that:

1. Embryos do not help each other to implant. Their chance of implantation is completely independent of each other.
2. Transferring a blastocyst in itself carries a 5% risk of monozygotic twinning (identical twins)
3. Transferring more than one embryo, greatly increases the chance of twins (and triplets see #2 above). This often leads to premature birth with potentially lifelong consequences, sometimes not apparent until the child goes to school. 
4. If twin pregnancy occurs and one of the embryos is chromosomally abnormal but does not vanish on its own, the surgical intervention to stop its development may affect a healthy embryo. 

Bottom line: there are no justifications to ever transfer more than one embryo at a time.