25 year-old red oak throughout most of house.

We would like to convert two carpeted rooms (maybe even just one) to red oak to match the existing, and make it look as one, or as close as possible. We were told (of course) we would need to sand, stain/refinish the existing oak in order to match the new stuff.
Which of course triples the price.

But do we have to? Does this always, always have to be done - or is it somewhat of a scam perpetrated by the flooring companies? It still won't look perfectly the same anyway, will it?
What if we try to match the existing wood and stain as close as possible, and forget about redoing the existing? maybe run a rug from old to new?

Anybody have a photo? - old finished wood next to new finished wood (without the old being re-done) -
Thanks folks

If the new flooring runs parallel to the old flooring you have a chance to match the stain of the old floor. Old flooring has a patina from light affecting the surface that is very hard to match. The new flooring will be brighter if the old stain formula was used, until light has affected the surface for a long time, months or years. If the new floor is stained to match the old floor perfectly, the color will change from the perfect match to a patinated color over time which will be close but still noticeable. If you do not want to sand the old with the new, you can try to match the color then add a coat of finish to the old floor when applying the final coat on the new floor so that the sheen of the surface matches. This would be the most practical, if the old floor has never been waxed. Do you know? Have you been the party that has maintained the old floor? There may be an adhesion problem with the final coat of the new flooring adhering to the old floor finish.
Sanding both parts of the room at once is the best value in the long run, using the same color of stain on both, which may not be a perfect match but close enough to be acceptable. Wait 6 weeks to put area rugs down to minimize the photo effect on newly sanded floors. You will get a photo the shape of the outline of the area rug over time that is more pronounced if the floor is covered after the full cure instead of waiting.