I normally don't try to push a buyer away from what they have their heart set on. But, PearlParadise has a wonderful strand for a 10th of what you are planning to spend. AAA quality freshwaters in a larger size. I think it's at least worth a look.
http://www.pearlparadise.com/detail.aspx?ID=2233
Or, you can get this longer rope with larger pearls in a better quality from The Pearl Outlet and have enough left over to buy yourself and me a strand too.
http://www.thepearloutlet.com/servle...supplierID=490
Or, for just a bit more, The Pearl Outlet will customize two strands of Hanadama for your mother. Now that's bling!
I think what I'm trying to say is, when you buy Mikimotos, you are paying a huge premium for the name but you aren't getting quality for your money.
Shop a bit before you spend. Mikimoto is not the only place to buy pearls, nor is it the best place to shop.