I finished 2018 with 77K miles, but $1300 short of spend for Platinum. Received my 'custom' buy-up offer yesterday. They want a cash fee of $1700 for Platinum. I was 1K for years, until the spend requirement did me in. Then Platinum for 3 years, but in 2018 I just did not fly enough to meet the spend. And without GPUs, there was no point (if there had ever been) of buying a higher fare on the off chance of an upgrade.
I will pass on their offer. I have much better ways to spend $1700, and the difference between Gold and Plat for international flying is too small.