There will always be outlier sales where there is a (strangely) motivated buyer. With something as unique as domains (there are no 2 the same) you cannot realistically set a method for evaluation. This is why paid appraisals are worthless. However there are *types* of domains that are more likely to sell. We go for these.
Of course the type of domain is not the only factor. If a group of people had exactly the same domain and there was a potential buyer, some would get no sale, some would get a good sale, and some would get an excellent sale. All domain sales fall into the same category. How much is the domain worth to me? A seller has their idea and a buyer has theirs. The point at which both ideas intersect is the sales price. I personally like domains that have 3 or more potential buyers or have mass appeal for various reasons. If you have to rely on one potential client or a 'lottery' sale then it's not going to be a long successful business.
Taking your example above vowtobechic.com is an awful domain. 'Vow to be chic'. Who says that? Why would I prefer that over 'Promise to be chic' or 'Vow to be suave' etc What is it about that domain that commands a premium price? So if you were investing in those types of domains you could spend all your money very quickly on domains equally as poor that will never sell.
FlashSale immediately tells me what it could be used for, what I would be likely to find there, and is way better. I could see a route to development, potential monetisation ideas, etc That doesn't mean I want it just that there are going to be more people that do than the terrible one I mentioned above.
I say it many many times and it is an important lesson for everyone in the market. 'Asking price is NO indication of the value of a domain'. I can ask a million for my house - it's not worth that. It doesn't mean my house is worth a million because I said it was. Look at sales, not asking prices.