first of all I agree 100% that the interior matters as much as the exterior - the world abounds with reps that look fine on the outside, only to cause severe brain-pain as soon as a door gets opened - that said, even on a budget, exemplary results can (and must) be achieved. As already pointed out, one can find myriad examples of excellent seats online but it doesn't have to stop there.
So many funky elements can be fabricated or picked from other cars (I LOVE WRECKING YARDS!) to make yours a unique and beautiful interior, while firmly adhering to a modest budget. I did it on a 74 911 that I rebuilt into a 1993 3.6 litre twin turbo replica - those who know Porkers from that era know that their interiors were almost an afterthought, so it wasn't that hard to do a better job that original. The most expensive element was the flashing LED door locks and even then I opted to NOT buy the ribbed ones from the 1993 vehicle but instead bought the ones from a lesser model - when in the down position they were exactly the same thing and literally were a tenth of the price.
So .... I reckon do precisely what you're doing, get great advice from the guys here and elsewhere - check out uber-funky interior elements from a range of cars and make an interior to die for that doesn't kill your budget. It's all possibly - lots of folks have don it.
I am now off to see what's so special about the seats and have a think about what might look good instead