Here the current prices for processors:
$244 - Athlon XP 1900
$181 - Athlon XP 1800
$136 - Athlon XP 1700
$113 - Athlon XP 1600
$108 - Athlon XP 1500
$259 - Athlon MP 1800
$168 - Athlon MP 1600
$158 - Athlon MP 1500
$153 - Athlon MP 1.2GHz
$147 - Athlon MP 1GHz
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$78 - Duron 1.1GHz
$59 - Duron 1GHz
$45 - Duron 950
$39 - Duron 900
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$409 - Pentium 4 2.0GHz
$265 - Pentium 4 1.9GHz
$205 - Pentium 4 1.8GHz
$193 - Pentium 4 1.7GHz Sock 478
$165 - Pentium 4 1.7GHz
$153 - Pentium 4 1.6GHz
$148 - Pentium 4 1.5GHz
$105 - Pentium 4 1.4GHz
$97 - Pentium 4 1.3GHz
Prices provided by Pricewatch