Not knowing either one all I can say is when it comes to buying things online the entire spirit of it has changed over the last few years.
Where people once only listed something for sale in one or maybe two places, they now list them in multiple. And, they don't pull them down right away as they should post sale.
If you wish to buy them and then later someone comes in with an offer that is better than yours you're going to get the old school Craigslist treatment. Craigslist was famous for having sellers not sell to people they committed to selling to because they received a better offer after agreeing to a deal.
The only way to avoid this angst is not to play the game. Don't buy online if you don't want to risk disappointment and potential outrage.