Is there a way to sell the estates/
Welcome to TUG
You may wish to look at Aimfair - a Vidanta owners group that has lots of Vidanta news and has "for sale listings."
There is also Redweek.[ both require a small annual membership cost]
However as
@tschwa2 has pointed out - there is the Vidanta transfer fee listed in your ownership documents
There is also language in your contract that will remove benefits if the contract is transferred to non family .
[ Family transfers [children / grandchildren] are free and the transfer retains benefits]
If your contract has the " Pay on Use Only " addendum - then your on-going cost is $ 0 [unless used]
& the contract will end if you don't pay the next renewal [ typically due every 10 years & typically at the cost of current MF / Usage Fee.]
Unfortunately the money you paid to buy is [mostly or entirely] " sunk money" .
I would expect that even if you found a buyer and sold the contract - your net dollars received would be at least 95% less** than you paid.
**[ This is a guess on my part based on much reading of TUG & the TUG Mexican Forum ]