Hi mojcasss,
Generally speaking you will get more for your money with freshwater pearls.
? The highest grade freshwater pearls are very lustrous. Some even have a metallic luster that is similar to the luster of akoya pearls.
? Most freshwater pearls are all nacre-- no bead inside. Akoya pearls have a bead nucleus that is covered with nacre.
? Even if you prefer to buy akoya pearls, remember that with Mikimoto you are paying for the brand name. Incidentally, grade A is their second-to-lowest grade (A1 being lower).
Are you sure you want earrings that size? 7mm is good for a younger girl or someone with petite ears or for an everyday pair (it's harder to use the phone while wearing large studs). But many of us prefer a larger size. With freshwaters you can go larger for the same (or less) money.
Here are some to look at (vendors are members of Pearl-Guide):
In the UK:
Pearlescence.com
akoyas:
http://www.pearlescence.co.uk/product_info.php/cPath/193_251_256/products_id/1062
freshwaters (scroll down to the studs):
http://www.pearlescence.co.uk/index.php/cPath/104_176/sort/2a/page/2
In the USA:
Pearl Paradise.com:
http://www.pearlparadise.com/c-47-white-pearl-earrings.aspx
Pearls of Joy.com:
http://www.pearlsofjoy.com/Pearl-Earrings_c_17.html
Pure Pearls.com:
http://www.purepearls.com/pearl-earrings/by-color/white-pearl-earrings.html