My GSD had cancer, but not hemangiosarcoma. I went the chemo route. Without chemo he had a life expectancy of 3-6 months, with chemo, 1-2 years.
My GSD was a big boy, and chemo is charged by the pound of the dog and it was extremely expensive overall. There are many different types of chemo, some cheaper, some pricier. Cancer can build up a resistance to chemos, and you may have to use a variety of chemos, even return to ones that you had used before. It is very complicated.
Chemo for dogs is different than what they do for people. For dogs, they do it to extend quality of life, for people the goal is to cure. With that in mind, the amount of chemo used in dogs is far less than what they would give a human, therefore there tends to be far less side effects. My dog, despite a variety of chemos, had no side effects to any of them that impacted the quality of his life except for one bad day.
My dog lived another quality year, lots of love, hikes, food, hugs, swimming, you name it. His last two weeks of life weren't so good as the cancer began to beat him down, the chemo did not work anymore, and I had to let him go.
If I had to do it over and money were no object, I would not hesitate.
I would discuss the costs with your vets, you may find some chemo options very affordable.