I agree $150/month sounds a bit on the high side. Before you buy a policy I would recommend looking up your info on the Social Security website to see how much they would pay out if you became disabled. For me it's something like 25% of my salary. That might not sound like much, but since I'm Mustachian and live below my means, that amount would actually pay for the majority of my typical spending.
Remember, though, that
if you become disabled your typical spending will change, and not for the better.
You will have a lot more copays/coinsurance/etc. for health care, since you'll probably have to go to the doctor and/or nurse and/or physical therapy appointments much more often (random example: if you're ever in a wheelchair, you will almost certainly develop the occasional bedsore and require some nursing visits and some skin-care doctor visits).
You will probably need some medical equipment, you may need some home renovations and/or some replacement items (e.g. if you can't use normal silverware, you'll need special silverware--which isn't cheap).
You may need a service animal--just getting one is a big expense, and then you have to feed it and give it good veterinary care.
You may need to drive or take the cab to places you currently walk. And/or you may need to retrofit your car, or replace it with one that's already retrofitted, to enable you to drive it--or even to ride in it (some disabilities can prevent you from sitting in a normal passenger seat).
You may need to hire someone to do tasks or errands that you currently handle yourself. And so on and so forth.
Disability insurance seems like a good thing not to skimp on. Social Security Disability Insurance is pretty bare-bones, and of course nowhere near salary-replacement levels.