Depends on which ones will meet your needs for hills and size area. If one doesn't meet those needs, it doesn't matter how cheap it is. For example, hand sheers are fairly cheap, have low operating cost, and if you maintain them regularly, they can last a long time. But, this may only be suitable if your hills are only a few square feet. My point here is that perhaps it is best to identify which ones will do the job at the comfort level you desire, and then compare prices.
If the hills are shallow, ground fairly smooth, and the area not too large, then just about any could do. But, if your hills are fairly steep, ground is uneven, lots of area to cover, perhaps many obstacles to go around, then the cheapest ones may not be suitable. For steeper hills, I would suggest looking at how good the traction and side stability is. I has a cheap craftsman and it felt very unstable on the hills. After a couple years, I stepped up to a garden tractor and it did substantially better on the hills (with chains on all the time), but still had areas where it felt unstable. Finally, last year, I stepped up to AWD and 4 wheel steer. Cost is high, but this machine really hugs the hills without chains.