broken timing belt,how much are the repairs?

Can't estimate with out knowing how much damage was done. On some cars with interference engines, the valves bend and a replacement head is needed. On some cars, the pistons are damaged and a replacement motor is installed. --- A used motor should be around $1250-$2000 installed. It could be more - that is a real rough number. --- Assess the damage and get real estimates from your local shops

The 2008 Mazda CX 7 Sport has a 4 cylinder 2.3L engine that has a timing chain. it's a Ford Duratec L3-VE or L3-DE...what happened exactly that made you think it broke? Are you confusing it with the serpentine drive belt?

And if so, if you do it yourself, inexpensive

DavidH25 - a similar thing happened to a car that I intend to buy 2007 Mazda CX7, the car is not staring now and it was left aside for 6/ 7 weeks. I was told the lady was driving the car on a highway and the car suddenly started slowing down and she managed to stop on the shoulder and had it towed to a mechanic shop that advised that it could be that the timing chain fell. I have read other posts mentioning that the damaged timing chain in the CX7 will also effect the VVT. is that tight? My main question is with the way the CX7 motor is designed what are the possibilities of this problem causing damages to the pistons or the valves. I was told the chain foul cause valve damage on some types of motors but could cause pistons damage on others. Thank you in advance...