Matching Numbers and resale value

I think if it is an unrestored car the price would be less, but the percentage higher. Where a restored car the price would be much higher, but the percentage would be less. Just my opinion but I think only a collector/investor, looking at an original unrestored car, would value the matching numbers engine at 30%. I just can't see a perfect restoration with a sale price around say, $27K, sell for $20K because the engine isn't matching. But I could definitely see a restorable but unrestored car, selling around $8K, selling for $6K because of the non numbers engine in it.