The time it's taken them isn't part of the equation. The important thing is what the contract dictates and if the home in question is still under contract for you to purchase. The per diem is spelled out in the contract so you need to read the contract and it will tell you the answer. If you have any confusion after that you should ask your realtor and/or your attorney. Good Luck.
If in doubt, it's always good to seek the advice of an attorney. Just because you found a better deal does not relieve you of your obligations under a contract. There are other mitigating factors as well, but the most obvious one will be the dates on the contract. It is NOT a good idea to move forward with another home until you know for sure you are out of contract with the first one. You could end up buying two homes! Be careful!