ND useful when u wanna shoot long shutters in bright light...
maybe u want the foamy waterfall in 1s in the day time... even using 50 film u can't get it? so u attach 1 or 2 ND8 filters, voila tripod time!
wide angle 2nd hand usually ard 600 for a good one, 1k++ for L-ish lens, or 300 new for a cheapo one...