Dont worry so much about the cost. Some joins can be done with fk/pk, and some joins cannot. That is just a fact of life when it comes to meeting the requirements of the business solution you are trying to achieve.

More important than the cost is the actual run time of the query. If the cost is small, but the runtime is hours - then your customers wont be too happy when you say "But the cost is really small" :-)

Your query looks fine to me. Inequality joins can be hard to optimize when the data volumes get big, but worry about that when the time comes.

(And thank you for providing a test case)