In buying regs, I would be more inclined to look at the cost of ownership over at least 5 years. Not just 2. If you gave free service for life, then 2 years versus 5 years probably wouldn't matter. But when you only give the first service for free, doing a cost analysis for 2 years is really going to skew the equation in your favor. I don't buy regs to be replaced every 2 years.
I don't think just looking at it over 2 years versus 5 changes anything. But lets do the math on 5 years of service of the packages you presented.
Ours:
$835 for regulator set
First service free at 2yr mark both labor and parts
Second service at 4yr mark - kits cost $75.00, or with a service plan through us they are free.
Total cost $910 - first labor free, shipping extra.
Theirs:
$749 for regulator set
$101 for service kits at 2yr mark plus labor
$101 for service kits at 4yr mark plus labor
Total cost $951 plus labor at both intervals.
$1052 would be approximate if using your example single tank service cost above.
Continuing this on at the 6yr, 8yr, etc mark and the prices will diverge further, based on the cost of service kits, even if labor was the same, or not needed (servicing your own).
I would not get the free service because I'm now a DM for a shop and I'm pretty sure they'll service my regs for no charge.
The kits still cost $75 versus $101, excluding the labor.
Even if I were not a DM, I would be looking at $105 for a service versus some amount of money for shipping, the risk of shipping, the risk of needing post-service service, and the total time I would be without my regs. I don't know what the shipping and insurance would actually cost me, but there is a good chance I would just pay the $105 to have it done locally and know my regs would have no risk of getting lost, could be done and back in my hands more quickly, and I could take them back to the service tech easily if there was anything about the result that I wanted changed. The last time I had my DR regs serviced, there ended up being some problem with one of the parts (from a new service kit) that was installed. After a couple of uses, I was getting severe IP creep. I took them back and they fixed them (installed another new service kit) - quickly and for no charge.
Service plans with us have them turned around sooner than most local dive shops get around to them, in most cases customers would be without their regs for less time than the local shop would take to service them, including shipping time. It is why we are offering direct service through us. But you could also get any local affiliate who is trained to service them for you, order the parts and service yourself, or get the parts and have your local tech service them, our service manual will be freely posted online. Sending them to us, the cost would be lower, servicing with a local affiliate/tech would be up to what the price is, but considering the labor is probably the same, and the parts kits are less expensive, I imagine it would cost a little less.
If there is a problem post-service, we will happily fix it and return to you no charge. Our service plans will include servicing when you need it, not only at the 2 year interval. That alone can end up being a fairly good deal if you dive a lot.
A pure financial analysis would almost certainly be in favor of sending them off for the free service. But, if it only costs me an extra, say $50, to have it done at my local shop, then I view that extra $50 as ensuring that my regs won't get lost, ensuring convenience if I need post-service service, ensuring I get them back sooner, and lastly, giving support to my local shop, which I really want to be around for a while.
The regs are insured for shipping, but yes if you think you can get them done locally for only $50 more and turned around within a week, then go for it. But regardless of brand, you should be able to find a reliable local tech to service gear. I think it is important to find such a person if you don't want to service yourself or send back to the factory for service.
Regardless of the above, I plan to do like a lot of tech divers and learn to service my own regs as soon as I can. Once I do that, I will service my own regs.
So, a raft of potential reasons that anyone might not take advantage of the free service offer.
I service my own regs, and encourage all tech divers to do the same. It is just good practice to know if you plan on doing a lot of tech diving, a lot of diving in general, or maintaining a large collection of equipment. To that end, we try to keep our costs for service parts as reasonable as possible, as this helps reduce overall cost for guys who do it on their own. We don't require anyone use the service plans, its just an option we offer.