What is the points cost for space marines?

There are many different types of space marines, so thus there is no straight answer. Spacemarine terminators in unit of 5 and a terminator sergeant are 200pts. You can then add 5 extra terminators for 40pt per model. Assault Marines come in at minimum, groups of five, and that is 100 points. Additional Marines after that cost 18 points. There are many others, and you may consider buying a space marine codex if you want all of them.