I recently booked a stay in Prague which seemed positive, with quite a large number of positive reviews. Normally with all my other airbnb stays, I contact the host many days before and organise a way to check in and a time. This has worked out well, we simply meet at a specified time, talk and get given the keys and shown around the place. Back to the story in Prague, I contact the host 4 days prior to check in and receive no reply for those 4 days. The listing on the website becomes 'disabled' and the last calendar activity of the host is 6 weeks ago. There are then reports saying that previous tenants where 'bumped' to a different apartment as there was a problem with the listed apartment. This raises alarm bells to me and the last thing I want to do is arrive in a foreign country and be left stranded. Which is exactly what happened. I contacted AirBNB a day prior to the event detailing the 'fishiness' via online medium and have only received automated replies.
Luckily our host in a previous city had a friend who could arrange us a stay at short notice. Don't get me wrong, people are people and there are fantastic people out there.
So really the price difference is a multitude of services, and how much you will risk being stranded or mislead.