It really depends on the combat stats. You will get the most for old school accounts if they are combat 3. And if they have combat stats, you will get the most for 1 defence 1 prayer.
Old school accounts mainly have around 45 attack, 50 strength, 45 defence, 20 ranged, 30 magic, 48 hitpoints, 32 prayer I'd say. I think everyone used to bury bones as a noob and you really see a lot of accounts with the stats above.
No idea what your stats are. Can't do a proper PC now but if it's a combat 3 you can probably get ~5m, if it's a 1 def/1 pray pure you can probably get ~3.5m and if it's a random main you can get ~2m.
Just my estimates though.