The correct pricing for an item of infinite magic missiles would be as follows:
spell level (1) x caster level (1, 3, 5, 7, or 9) x 2000gp. the footnote covers extra cost for continuous items based on duration of the base effect, but they oddly did not mention instantaneous, so such effects seem to get off the hook. your total cost would be: 1 missile = 2000gp, 2 missiles = 6000gp, 3 missiles = 10,000gp, 4 missiles = 14,000gp, and 5 missiles = 18,000gp. only an arcane caster can (normally) create such an item. This assumes some sort of hand-held point & shoot item - that is technically not a wand. slot-less will cost you more.
now, in my opinion, that is a bit pricey, for such low level damage, despite it being up to 5 strikes per round. i might discount the higher priced ones on a sliding scale.