I haven't had the 14 day version for a long-term test drive to write a review. I've only had it on my wrist.
It has to do with Vacheron Constantin's long term strategy. It's a bit too complex to give you a comprehensive reason why the 14 day is so much more expensive. And even if I did, you may not find it entirely justifiable.
Here are the main reasons why the 14 day is so much more expensive.
1. 14 day was launched back in a time when Patek Philippe and Vacheron Constantin, two of the most prestigious watch companies, simply charged a lot more for a tourbillon. Patek Philippe had a 10 day Tourbillon that was priced at a certain price, and Vacheron Constantin had one that was priced at a similar level. If Vacheron Constantin priced theirs at a much lower level, it would indicate that their brand was inferior to Patek Philippe's.
2. Fast forward to today, Vacheron Constantin has developed a really cool tourbillon movement, the 6000T. This movement was made for the modern consumer in mind. Modern consumers generally like automatic watches. The appreciation of the tourbillon has also shifted. Tourbillon complication has become more mass market. JLC made a $50K tourbillon automatic that has sold in the highest quantities ever broached for a tourbillon. Vacheron Constantin has made an automatic tourbillon where the rotor doesn't block the tourbillon. They've priced it significantly lower but still in a very high strata. It's still an excellent watch and it's designed to appeal to a broader market, especially in USA and Asia. They're also releasing this tourbillon movement in the Traditionelle Collection, the Overseas Collection, and the FIFTY-SIX Collection. It's going to be a higher volume tourbillon.
3. Again, I haven't compared the 14 day tourbillon vs the new automatic tourbillon. But I do recognize one does cost 2X more than the other. How does VC justify this? Is the newer tourbillon inferior in some way? Is a 14 day power reserve really worth double the price? The answer to the past two questions is "no." But VC is just trying to expand the market on tourbillons. They're trying to capture a niche of the market between JLC's lower priced $50K tourbillon and these upper echelon tourbillons from Patek Philippe, Audemars Piguet, Lange, and even their own Vacheron Constantin branded tourbillons that were all priced in the $200K range. So they found a niche in the $110K range and built a wonderful tourbillon for that market.
4. Is the new tourbillon cheaper to build than the older 14-day version? Probably! Easier to build? Likely! If it takes less time to build, does that mean it's inferior? Not necessarily. Rationale: Everything recently designed is designed to be easier to build, adjust, and service. Everyone draws from experience to build a better product. Basically it's like technology. 20 years ago, computers were expensive, poor performance, and not very capable. Today, computers are designed better, manufacturing systems have improved, computers perform better with better reliability, and they even cost less! Tourbillons maybe benefit in some similar fashion.