I have a 4 room multi-dvr and wanted to know what is costs to have 2 rooms with multi-dvr and the other 2 just HD stb's?
It doesn't work that way, because the MRDVR (multi-room DVR) serves all STB (set top boxes) on the network. You are not charged for MRDVR based on the number of units it serves (although of course you do pay separately for renting each box on the network). Instead you are charged for the MRDVR as a unit.
Note that because all your other boxes are HD (I presume) you will still be able to view all the MRDVR content on any of your existing STBs. Hope this addresses your issue as well as I understand the situation. Good luck.
In case this is helpful to others here - I want to add that MRDVR physical box itself only costs more if you actually have other DVR's in your home. Specifically - I did have a second DVR in my home, decided to disconnect that TV and return the DVR. It was NOT necessary for me to return my MRDVR box; the multi-room capability was just terminated by Verizon (no impact on equipment in my home). And billing was adjusted so I'm now just paying same as a single regular DVR.
That was great - since I didn't have to lose the recordings I had stored on my MRDVR unit.