For a 3.5 HP router I think I would prefer to use Birch or another type of hardwood ply for the table top with an aluminum or steel insert plate. As already described making your own table is as complicated as you want it to be. But all in all its pretty simple. Making your own can accomplish more then just saving a little money as well. Its a skill builder. If you have never, you will learn how to use patterns, and pattern bits, as well as how to cut a dado, and how to perform certain joinery tasks when building your cabinet.
It really just depends on you as the end user though.
You could buy a Ryobi intermediate router table for $99, and install a steel or aluminum plate for $50.00 with an aluminum miter track for another $15 like I chose to ( because I used what I had mainly and its very portable ). The router was $59, table was $99, plate was $50, miter track was $15.00 so $223 later I had a good portable table with vacuum port, shimmable fence for jointing, T-trac and feather board, bit guard, miter gauge, Lam' MDF top, a power switch with two outlets, and I can change bits or adjust height all from above the table. For me
, going that route was much cheaper then buying the OP table, or any other on the market right now, even buying the materials to make one from scratch.