Yes this is low but it's similar to what I'm seeing. In the end, is the rate good enough after expenses?
Also as stated, it's "per day" but nearly everyone calculates it by the hour. Double check the offered rate against the IRS tables and the actual costs that you would incur to see if it adds up.
Finally in this economy, I'd ask what happens to the per diem if work slows down? Say they cut back to 32 hours / week. If it's too far to commute back home, your hotel is still charging you but you're not getting a full weeks per diem.
And yes, they are saving money on taxes, so they are doing themselves a favor as well. The implications for you are how will the "per diem" dollars impact your taxes, social security and now unemployment calculations (that economy thing again).