It's late and I'm tired so no math for me! But...
I LOVE the necklace in pic #6 (that's the lapis?).
The other necklace (#5) is okay, but similar in that it's gold + blue. If it's much more expensive, I vote pass in favor of #6.
You need a purse if you haven't bought one in 4 years. Conundrum. I like the color of this one especially with the jewelry coordination. I.e., they are like a pair. If you can only afford one or the other, that is a tough call.
As for the boots... I'll be the naysayer... I think they are too tall. Love the wedge and sleekness, but worry they are hitting you too high. Did you try sitting in them? Did the top of the boot rub the back of your knee when you sat? I.e., the driving test? Boots that tall on me would snag the car seat when I'd attempt to brake. Of course you could get them shortened by a cobbler, but that's additional $. Then there's practicality. But yeah..... then there's comfort, and for comfortable shoes, I would invest there first in a heartbeat!
Okay to add to your math equation, I'll tell you that a few months ago while in Sedona I splurged on an $800 moonstone bib necklace. The most expensive piece of jewelry I now own, not counting my wedding set. It just called to me on so many levels. It was barely a debate in my head. I am happy to say I have worn that necklace constantly -- several times a week. It goes with everything, as statement making as it is. It's fast becoming a signature item in my wardrobe. No regrets.