I’ve always been of the opinion that late model used cars are back on the market for a reason. In many cases that reason is that they need some expensive work, have an insolvable problem, or have been in a wreck.
$11,000 is one heck of a lot more money than $1,500. If the car has otherwise been good to you, IMHO you’d be foolish to spend many thousands of dollars replacing this one rather than spending $1500 repairing it. $11,000 vs. $1,500. Compare.
As extremely unusual as this is, I can’t totally agree with Cig. Some engines do tend to use more oil than others, and it’s deposition onto the catalyst that causes deterioration in efficiency. In short, some engines will use up a cat converter over time. In other engines cat converters last forever. I personally would not consider a cat converter at 98,000 miles to necessarily be a sign of any internal problem. If you’re also using excessive oil, more than a quart every 1,000 miles, or you have other signs such as an oil-soaked sparkplug, then I’d get serious.