The price range for 'good' espresso grinders is somewhat higher than that, unfortunately, more in the realm of the Gaggia MDF which is a good chunk out of your desired price range. Trying to spend even less than $100 is going to result in a very poor and inadequate grinder.
From accounts, the MM simply doesn't do a wonderful job for espresso. However, while you would still like the best ground coffee for any machine, the Breville will be less sensitive to this due to its (I believe) pressurized system. Same caveats apply as before. Better ground coffee --> better tasting espresso. Pressurized portafilter --> less tasty espresso.
In between the MM and the MDF you will find some of the plastic-housed grinders based on a common conical burr set. Pricing varies, but some grinders like the Nemox/Lux, LaPavoni PGC, Maximo (like a LaPavoni), or I hesitate to say Innova grind very well. Some have more flimsy plastic parts which can break easily, as we found with the Innova and has been said for the Maximo. You can see an unhappy review of the Innova's problems here in 'The Daily.' There has been some small fuss about the low price of the Maximo at a US vendor (found easily enough with google).