I'm a betting trader, we don't set the odds you do by choosing which outcome to put your money on. The more money that goes on a particular outcome the lower the odds of that outcome becomes. It has to be that way because we work on something called an overround, essentially this means the odds are adjusted so whatever the actual outcome is we make the same profit.
The difference in odds of us winning the league and being relegated are irrelevant because those two markets are independent of each other.
The true odds of a market are more indicative at betting exchanges where the odds are set by traders buying and selling each side of the market at a price others are willing to accept (in much the same way stocks are bought and sold).
If you look at the trades for the two markets you mention you will see that they are not that dissimilar to the odds at the bookies.
https://www.betfair.com/exchange/plus/football/market/1.229393513
The truth of it is that if we were 2000/1 we would have taken on a lot more liability than we have, people would have then layed off their bets at the exchange for a huge profit and currently be sunning themselves on their private island in the Caribbean!