There are plenty of Glocks for sale in MA, if you hang around here long enough and cough up the money for a membership you will find them in the classifieds all the time.
The chances of a MA FFL accepting a transfer from out of state is near zero... sure there are some shops that will do it, but there are other easier ways to get one in MA, including Gen5's
As I mentioned previously, any rifle you bring into MA has to be MA AWB compliant, and again for what little a dealer makes on a gun, it isn't worth the hassle of doing a transfer into MA and dealing with the BS
There was one member here who did a FFL to FFL transfer of a Glock from NH into MA, without the high capacity magazines, by using one of the work arounds we don't mention publicly. I don't think he would do it a second time though as it was kind of a royal PITA.
Don't get me wrong, I think Glocks are the Toyotas of firearms, well maybe not the .40 stuff with the setback issues, but I digress.
But they are not worth a huge premium over MSRP
For example I am a big fan of the 43X, but they are not readily available at your LGS ( there are a couple in our classifieds iirc) but the Sig P365's are available and they are a decent gun for reasonable money...
But in our classifieds right now there is a pristine Model 26, and a nice (if you like OD Green) Model 17 Gen3 being offered by a well respected member for reasonable money..... in fact pretty short money as far as Glocks go in MA.