I think your math is pretty close assuming you ended up with 1200 points every year.
You started with 1000 points every other year... which is equivalent to 500 points every year. You upgraded to 1200 points every year thus an increase of 700 points every year. $11,000/700 = $15.71 per point.
Your initial purchase was for $7900 points plus the upgrade for $11,000 = $18,900 total for 1200 points every year which is an average of $15.75 per point for your full membership.
Gold memberships are hard to find on the resale market...but there are some available. A cursory look finds a lot of summer weeks which aren't very interesting but ....There is a Gold Winter one bedroom listed on TUG Marketplace for $1800 under VDP Flamingos...At Redweek under VDP Cabo a Gold Winter One Bedroom for $3,500 and a Gold Winter Two bedroom for $4,000. Also a Gold Winter Holiday Two bedroom at $6,500. I quit looking after that...I'm sure there are more if you keep hunting. Remember, Gold membership do not have home resorts so it doesn't matter which resort they are listed under. The key is a winter season Gold week of the size you desire. These are not as cheap as back in 2010-2012 after the Great Recession...but probably still good value.
FWIW
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