I don't follow your maths.
27 X $900 = $24,300
75,000 points is say half a J return to Europe = say $ 2000-$4000.
I personally do not value points at full retail J Fare as I would, if I had to buy, shop around for a "special" price.
ie one could fly Emirate J return to Brussels for $3500 return on a recent special (very time limited though), though this was unusually cheap and so I would value points as worth more than this one example.
Sorry I should have been clearer. I'm not talking so much about what 75k points could get you, but rather how much money you would need to spend to get 75k points.
On my current Platinum Edge, I get 3x points for $1 spent at major supermarkets. If for some freak reason I spent all my money at supermarkets, I would need to spend $25,000 to get that many points. Hence it being "worth" 27 years in membership fees.
Under normal circumstances, I would need to spend around $38,500 to get 75k points (assuming average of 2 points for $1 spent).
Not sure if that makes sense - but in short when I think about the value of free bonus points, I think about how much money I would need to spend to get those points if I were just spending/flying normally.
This is a separate issue to how much those points are actually worth when it comes to spending them.