The easiest way to look at what it is costing you is assume the spread between direct and resale (~$75 for AKV) is invested at some rate of return and discounted at inflation. No need to consider the Dues since that is the exact same on each side of the analysis so would cancel out. You need to consider the reinvestment of that savings by going resale because that wasn't locked up in the DVC contract (so to make it apples to apples you need to lock that cash up in something). So lets assume 5% rate of return and 2% inflation (both conservative) tells me the cost of the $75 spread is equal to $75 * 1.05^37 / 1.02^37 = $219.21 per point (in 2020 dollars) over the entire length of the contract. If you want to average that over the entire contract life you get ~$5.92 a point bought. So that 100 point contract is really costing you ~$600 a year more (again in 2020 dollars). Though it really is less than $600 a year cause that averaging it out ignores again the investment income but for the sake of simplicity I'm ignoring it here.
Now you can start factoring in the benefits (DVC AP discounts, etc) to see if that ~$600 a year is worth it. But that $150 a year you determined ignored the opportunity value of that $75 spread that assuming you are paying cash for direct meant you had that $ to invest in long term appreciating assets to realize a return at the end of the 37 years.
I'm also someone that bought direct and resale so I'm not opposed to either but it is important to know the differences.
I don't really think the return on investment argument is a great one. With that logic you should skip DVC all together, wisely invest all that money and use your profits to book cash rooms.