Hi,

try this, post here if you find any other easy solution :

function field called permissions. group called fellow add those users into this group to whom you want field price as readonly.

    def _check_permissions(self, cr, uid, ids, field_name, arg, context):
    res = {}
    formid = ids[0]
    group_obj = self.pool.get('res.groups')
        group_ids = group_obj.search(cr, uid, [('name','=', 'Fellow')])
    group_obj = group_obj.browse(cr, uid, group_ids)
    group_users = len(fellow[0].users)
    i = 0
    while i < group_users : 
        if group_obj[0].users[i].id == uid : 
            res[formid] = True
        i = i + 1
    return res


'permissions': fields.function(_check_permissions, type='char', method=True, string="Permissions"),
'price': fields.float('Price'),


<field name="permissions" invisible="1"/>
<field name="price" attrs="{'readonly':[('permissions','=',True)]}"/>