It's quite simple really the technology is what's left over of a previously Advanced civilization stories of how to use the space traveling technology are passed down via oral tradition and there are Specialists that know how to use it but they don't know how to reproduce the technology. They don't and they know how to repair it ( fortunately equipment is well-designed it doesn't need repairs and won't for a thousand years) they just know the controls, this would explain El they could be a hunter gatherer Society and still used space travel.

First explain how a civilization has this technology. This is quite simple really the technology is what's left over of a previously Advanced civilization stories of how to use the space traveling technology are passed down via oral tradition and there are Specialists that know how to use it but they don't know how to reproduce the technology. They don't and they know how to repair it ( fortunately equipment is well-designed it doesn't need repairs and won't for a thousand years) they just know the controls, this would explain El they could be a hunter gatherer Society and still used space travel.

How to explain the expense. Well they may not know how to create the spacecraft they can remember how to make the fuel. Fortunately this fuel is made from plants and is simple to make even with hunter gatherer technology ( have no idea how this would be but what you say it is) so the expense is that most of the food is been used to power the spacecraft rather than being eaten by the people. Why haven't people revolted? Well unless the expense gets so high that the people themselves are starving I don't see this as being a problem the average peasant gave away 90% of crop to the Lord only keeping a little bit for himself to feed him and his family and trade.