I don't know why the price was different, but I paid 143.00 at the DL booth and 140.50 from the MWR. (I purchased 1 ticket at the DL booth and the others from MWR).
I live on the east coast and my nearest MWR did not have the DL tickets in stock, but they verified my ID card (in person) and sent my info to another MWR. The other MWR called me to get my CC info and then emailed me the tickets. It worked very well. So, you might check with your nearest MWR to see if they have a similar arrangement.
The only glitch I had was the vouchers could only be converted to tickets at the gate. We were staying at a Disney property and it took a few minutes to get the tickets issued on our early entry day.