score:6
You should consider buying an OV-chipkaart. With this, you can board any train, metro, or bus in almost the entire country and pay per kilometer of travel. It costs β¬7.50, however every time you have to buy a paper ticket for the NS train you pay β¬1 extra. Since you'll be buying around 20 paper tickets (Haarlem to Amsterdam/Rotterdam/The Hague and back for 10 days), it should save you a few bucks. Plus, if you come back in the next 5 years, you can use it again!
If you're planning on use the metro inside Amsterdam extensively, you can also consider getting a 1 to 7 day unlimited pass. This can be loaded onto an OV-chipkaart or used as a paper ticket. It only works on buses and trams inside Amsterdam though, so you'll still have to get an NS paper ticket or use the stored value on your OV-chipkaart to get into Amsterdam from Haarlem.