I own one MFT in my shop. So far it is still using its original top.
In addition to that my shop has 4 rolling work tables 4x10' with brakes on the casters. All of those tops are made from 4x10' birch or maple 19mm plywood that had some cosmetic blemish. When we find such sheets we put them aside. When time opens on our CNC nested router we turn those spare sheets into work surfaces with 20mm holes on 96mm centers. Writing the program took a few minutes. The CNC machines does the production in very little time. As a sacrificial surface for use with TS saws I much prefer good plywood rather than MDF or insulation.
I do keep a generous supply of 4x8' MDO on hand because that has proven to be the most effective sacrificial surface for the CNC nested router. That machine uses vacuum to hold the work in place. MDO protects the table top and allows better suction than does MDF.
As for cost, Festool uses something like HDF, a product I have no reason to buy in quantity. I deal with most of the leading lumber dealers in Southern California so I am sure I could buy it if needed. It would hardly surprise me if it turned out the cost of a Festool replacement top was 4 times the retail price of decent plywood or MDF. My question is how much time would it take you to drill all those holes in exactly the correct position? What would be the cost of sharpening the 20mm bit or drill?
I already own a 5x12' CNC nested router. Since I only make work surfaces during otherwise idle time, the only cost for the machine is the electricity. The router is 18.5hp and the hold-down vacuum is 40hp. So even a 5 minute run uses a bunch of KW, maybe USA$1.00. Because the CNC machine is turning the bit at exactly the ideal speed and feeding it appropriately, that bit seldom needs sharpening. However, if we were making those work surfaces for a customer, they would be expensive.
For the way I like to work, having such large work tops with holes makes everything go faster. We can position clamps as needed.