We aren't mate, I'm sorry but we aren't.
It's all very off topic now so I'm going to have dip out of it at this point. Please though, take an hour to read up about this stuff before going forward with it.
Let me give you on final example. I once saw a bloke go into a bookies and say 'I want a price, not just on Sam Allardyce to be the next Newcastle manager. but also the day and timing of his press conference'. He was utterly amazed that the major high street firm wouldn't lay him a price - surely it would be decent if he could be that specific? If you could do exact lengths and race time for a horse to win, surely those odds would be much better than a straight win??
Totally and utterly different markets. In a market like this, I would be amazed if any bookmaker would lay 100 bets at 50/1. Just would not happen. The price wouldn't 'go down' - the market would be suspended and artificially adjusted.
The example you give though are of Betfair which is slightly different to a regular bookie, as it simplifies the bet and makes it more like an exchange.
Bookies operate in two ways. 1) They have stats guys who assess the probability of something happening. 2) They then fluctuate their odds to cover themselves. As long as they cover their losses with bets on the other side they are happy. Their profit margin lies in the differences of the pay out.
They would probably only look to suspend the market if they felt information was available that in instance 1 they were overlooked by. A managers race is different to a match, because people can have insider knowledge that isn't about stats and probability. That's more the cause of a suspension in this instance. Stop the market, assess whether the deal had been done, and only open if they know it is still an on race.
The collapsing odds on a manager will mean that members of the public are betting on them. When you see that you do have to ask why? It may be because there is something in it, or alternatively it may be a bit of a dead end rumour.
The current odds give us some idea, but only some idea. 2 months ago it looked completely unrealistic. There is some thought into this but you will only start to see a serious market if Martinez is confirmed to be moving.