$5K could be too much for a Formula. It depends on condition. But at that price you better not have to put too much money into it. The problem is it takes just as much money to restore a Formula as a Trans Am. Usually, you don't get the money back out of a restored Trans Am. the Formula will give back less. And, you've got the stigma of having a clone Trans Am, not the real thing.
But, if you've ever driven a 78 Formula, you know how graceful the hood is from the drivers perspective. They're really nice cars.....but most people, given a choice, would rather have a Trans Am.
Before my daughter wrecked my pristine 78 Formula, I figured it was worth about $4K. It did need new seat covers and carpet, but otherwise the interior was perfect even the dash. Ashtray was never used and the console was perfect. The body was totally rust free.