I have a theory that they do offer much more than 10D x skill point. I have two players: OneHoop LV111 and Xomby LV97. When I first started OneHoop, I didn't know how the game worked so I would buy defense points whenever people started to be able to beat me off of the Rivals List. It was before the boss event (or before I knew about it, I missed a couple/few due to not knowing there was an update available), so I leveled quite a bit at that time sometimes just for the energy refill to keep attacking/PvE. Some issue made me turn to the internet and I found this place. I was reading some old threads based on things I was searching and was under the mistaken impression that the shark tank started at 85 so I started to camp OneHoop. I also read about ROI and started Xomby. I didn't play him as a ROI account very long however, as I decided it made more sense to grow income exponentially by doing the upgrade with the greatest net/UpgradeHour that I could afford. I also discovered that the shark tank didn't start until closer to level 185. From that time on, I played both accounts fairly similarly. I also read about and/or discovered mafia bracketing so that I stopped investing in defensive skill points.
Recently however, I have mafia'd up for battles and with the last one I didn't drop back down because there was not sufficient time in between to waste punching in codes. OneHoop is rarely robbed and loses attacks fairly regularly, while Xomby is walking the line of no-banking (robs plus attacks >10%, but <10% attacks alone). I am not confident that it is because of the difference in defensive skill points because there are quite a few strong players hovering below level 100 trying to stay in boss tier 4. Not everyone, but a lot of people zoom up to LV115 after breaking that barrier to get Missile Turrets and some other nice equipments. So their level of competition is different. OneHoop also has more snipers dens. I am going to build more snipers dens with Xomby, but have used his skill points on Defense the last couple of level ups (just in case).
This experience has also made me reevaluate my policy of not upgrading defensive buildings. I now find L2 or L3 to be acceptable time spent when saving for a larger money upgrade. I'd rather be upgrading IPH, but I also don't like being robbed.
Both accounts are at reasonable levels of energy/stamina before the LTQ, but I will continue buying defensive skill points with Xomby for the last 3 level ups and then re-evalueate from there. I will be investing OneHoops skill points toward energy... unless they continue with the low-level-building hunt that this last LTQ entailed.
Anyway, based upon my experience, your question is not as dumb as the answers that it has received.
M@
PS FWIW, Rob defense is usually much lower than profile defense, so the difference was likely more exaggerated than the numbers indicate.