It's very likely the previous owner decided to sell the car because they were given the same news at their last service and decided to put the money toward an upgrade themselves.
Changing a cambelt doesn't improve engine performance, it's a service item that unfortunately has a limited lifespan and can be expensive to replace.
Sellers don't always paint the complete picture when asked about their car's past service history and often centre on the positives rather than any pending high service costs.
I'm sure if $950 was spent on changing the cambelt prior to sale then it would have been highlighted by the seller, but as in your case it wasn't, then it's a matter of not mentioning it unless asked.
Legally the car only needed a Warrant of Fitness not more than one month old at time of sale. Items such as cambelts are not a check item on that inspection.
Genuine sellers are not bad people by not mentioning future service costs. It's up to any potential buyer to do the correct checks and ask the right questions to help avoid high service or repair costs a short time after purchase.
There are a number of service providers who carry out pre-purchase inspections, with cambelts high on their priority list to check.
If there is no label in the engine bay or notes in the service book indicating when the belt was replaced last and the car is over five years of age and travelled around 100K, there is usually a big cross entered on the inspection sheet.
Potential buyers can use this and any other information noted during the inspection to walk away, negotiate a reduction in the asking price or agreeing to purchase on condition the seller carries out the necessary work prior to handover.
So why is replacing a cambelt so expensive on a modern engine?
Many repairers have been burnt in the past by only replacing the cambelt as a way of helping reduce repair costs. The cambelt is not only the drive connection between the two main shafts in the engine (crankshaft and camshaft) but it also drives the water pump.
When a new belt is fitted and tensioned it is applying load to the water pump pulley and in layman's terms new mating with old can result in failure to the water pump bearing. Worst case scenario is damage to the new belt which can result in extensive and expensive engine repairs.
In recent times the industry has moved away from cambelts on petrol engines, replacing them with chains that have no recommended replacement intervals. They can still suffer from problems, due to lack of servicing mainly, and in general are a lot more expensive to replace than the rubber cambelt.
Bottom line is get the vehicle checked out before committing to purchase whether buying privately or from a licensed car dealer.
The cost of having a vehicle inspected could save you a lot of money in the long run. And don't forget while some sellers may not tell lies they don't always tell the truth either. The potential buyer needs to ask the right questions, or get the car checked thoroughly.
The positive you need to take out of this Kane, is once the belt is replaced it's good for another five years or 100K and the new set of wheels will no doubt be a lot safer on the open highways than the old Mitsi.