Why so many #'s for same o2?

Why does Toyota have so many part #'s (about 27-30)for the same single wire flange type bolt oxygen sensor used on most first generation EFI Toyota's?:

DAIHATSU
89465-87601-000
89465-87704-000

GM
94850731

Toyota
89425-19165
89425-69045
89465-02010
89465-19055
89465-19135
89465-19136
89465-19155
89465-19225
89465-19265
89465-19315
89465-19316
89465-19435
89465-29055
89465-29075
89465-29076
89465-29165
89465-29166
89465-29195
89465-29316
89465-29395
89465-39105
89465-39145
89465-39146
89465-39185
89465-39205

Denso aftermarket
234-1051

NTK
24105

I ask because when I type the part #'s at several online Toyota discount dealerships the prices range from $66 up to $350 for the same wire,according to Denso aftermarket and NTK (oxygen sensor division of NGK)they are all the same part.