The cost of changing from an L1 to an EB visa depends on how you do it. The choices are either adjustment of status or consular processing. Keep in mind that, traditionally, employers cover the costs of filing.
Adjustment of Status
I-140 filing fee: $700
I-485 filing fee: depending on your age, it could be anywhere from $750-$1,140.
Biometrics fee (sometimes not applicable): $85
Consular Processing
I-140 filing fee: $700
DS-260 immigrant application fee: $230
Biometrics fee (not always applicable): $85
Affidavit of Support fee (not always applicable): $88