Ah, but it is quite possible that they are only in the situation they are in because they are so niche and they have to focus on unnecessary new features in a vain attempt to get new business.

If you purchase them, you just focus on bug fixes and features you actually need. The developers might be great, you might find you need to get rid of management dead wood. Or it might be that you get a very nimble team who in all likelihood have been itching to fix bugs for years and yet who haven't been able to due to competing interests in the business.