They get bigger the more power I can generate - say I build a rail gun, then I can send you a very big rock. Or perhaps I'm really pissed. Hop on over to a passing asteroid and send you a kilometer sized care package.
If someone else holds the high ground and that high ground is some 200,000 miles away, you are going to have a very difficult up hill battle.
Those other weapons systems cheap or not you refer to just became ancient history.
Our junket to the moon, wonderful as it was, was a classic fascist venture designed to glorify the state. It was started by a spoiled rich playboy kid (JFK)who never did a damned piece of real work, yet pledged billions to that project, while betraying the Cuban exiles, thereby setting up the closest we have ever been to nuclear war. The priorities and the issues are the same as they were then. It astounds me that so-called conservatives think billions spent on space are somehow justified.