Why is SQLAlchemy insert with sqlite 25 times slower than using sqlite3 directly?

Why is this simple test case inserting 100,000 rows 25 times slower with SQLAlchemy than it is using the sqlite3 driver directly? I have seen similar slowdowns in real-world applications. Am I doing something wrong?

#!/usr/bin/env python
# Why is SQLAlchemy with SQLite so slow?
# Output from this program:
# SqlAlchemy: Total time for 100000 records 10.74 secs
# sqlite3:    Total time for 100000 records  0.40 secs


import time
import sqlite3

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String,  create_engine 
from sqlalchemy.orm import scoped_session, sessionmaker

Base = declarative_base()
DBSession = scoped_session(sessionmaker())

class Customer(Base):
    __tablename__ = "customer"
    id = Column(Integer, primary_key=True)
    name = Column(String(255))

def init_sqlalchemy(dbname = 'sqlite:///sqlalchemy.db'):
    engine  = create_engine(dbname, echo=False)
    DBSession.configure(bind=engine, autoflush=False, expire_on_commit=False)
    Base.metadata.drop_all(engine)
    Base.metadata.create_all(engine)

def test_sqlalchemy(n=100000):
    init_sqlalchemy()
    t0 = time.time()
    for i in range(n):
        customer = Customer()
        customer.name = 'NAME ' + str(i)
        DBSession.add(customer)
    DBSession.commit()
    print "SqlAlchemy: Total time for " + str(n) + " records " + str(time.time() - t0) + " secs"

def init_sqlite3(dbname):
    conn = sqlite3.connect(dbname)
    c = conn.cursor()
    c.execute("DROP TABLE IF EXISTS customer")
    c.execute("CREATE TABLE customer (id INTEGER NOT NULL, name VARCHAR(255), PRIMARY KEY(id))")
    conn.commit()
    return conn

def test_sqlite3(n=100000, dbname = 'sqlite3.db'):
    conn = init_sqlite3(dbname)
    c = conn.cursor()
    t0 = time.time()
    for i in range(n):
        row = ('NAME ' + str(i),)
        c.execute("INSERT INTO customer (name) VALUES (?)", row)
    conn.commit()
    print "sqlite3: Total time for " + str(n) + " records " + str(time.time() - t0) + " sec"

if __name__ == '__main__':
    test_sqlalchemy(100000)
    test_sqlite3(100000)

I have tried numerous variations (see http://pastebin.com/zCmzDraU )