My take: you get what you pay for.
The e-bay offer is definitely a "bargain", but I again reiterate that the identification of these parts does not mean they're Moog, and I see no claim that they are--again, the ID (using Moog numbers) is more a matter of "industry-standard", since Moog has such a large footprint in the business. It was very easy for other suppliers to adopt the same numbering just to avoid confusion on the other side of the parts counter with inventory control, etc...whether the customer knows or cares that the parts in question are top-line Moog or not (or even knows the difference) is an entirely different matter. More often than not, the average customer is going to opt for the lowest cost possible...even if it's known not to be a "top line" brand/source.
That said, in defense of ANY new parts vs a front end that is worn out, it SHOULD be an improvement to install new components to tighten the car up in the driveability department.
More expensive parts (assuming OE spec, not "performance enhancing" parts--such as DelALum bushings, etc), alone, will not necessarily provide any greater improvement in how the car's handling or feel is improved, initially, but 10,000 miles down the road, it might be clear that it would have been better to spend the extra $$ that the top-line parts would have cost.
There are so many things that can come into play--things that you aren't planning to replace during the rebuild--that there is no guarantee a front-end rebuild alone (steering linkage, ball joints, and control arm bushings) will be a 100% "cure-all". For example....the steering column lower support, intermediate shaft, and the steering gear itself--as well as questions like "is the frame 100% in spec?" (not bent, upper control arm mounting points are not shifted from frame sag, etc)--things that could easily be a problem on a 15 year old car with 100K or more miles of service, and could still leave the car with a "vague" feel, no matter how much you spent on the replacement parts for the "front end" job. And I should also state that you need to be sure that the BACK of the car is not contributing to a less than satisfying driving experience....that the tail isn't wagging the dog....due to rear control arm & bushing problems.
It's a complete package, and everything has to be "in spec" to again make driving the car a joy, not a chore.