these are entirely estimates and could be accurate or not, the real value of course is whatever someone is willing to pay for a name.
My (very rough) estimates:
JUSV.COM = $100
JJDE.COM = $75
JQQO.COM = $15 to $20
MPMO.COM = $250 to $500+
every now and then though some 4 letters go for big prices such as
SBSC.COM for $8,800
ZEBU.COM for $40,000
CESC.COM for $36,720
Although rare; if your letters fit an acronym that a big company or investor wants you may get lucky, I think your last name MPMO.COM has potential for mid $xxx to possibly low $xxxx or higher, those are good letters!
I've invested in a few 4 letter names and they seem to be good investments, best of luck!