Let me put this to bed (caster level 1 shield spell ring):
Use-activated or continuous magic item creation:Spell level x caster level x 2,000gp (x2 cost for spells with durations in minutes)
If my math is correct, a Ring of Shield spell with infinite uses cost a devastating....4,000gp
It is cheaper to have a friend create a ring for you or request one from a craftsman. You get a +4 shield bonus, activation or continuous, and it floats. The Force Shield ring is a stupid item that has no reason to exist unless floating shields spook people or something. You might as well put in a special order, what caster who can craft rings does not have access to the shield spell?