A Windows 10 license is about $50. What is the other $50?
To upgrade your iMac from base 8GB, 4x4 to 32GB is SIX HUNDRED DOLLARS.
Alternatively you can buy this aftermarket from Crucial, same timings, etc, for $139.98.
There is no earthly way that can possibly be justified - a four hundred and thirty per cent mark up on retail prices - even more when you consider the after market lets you keep the original 8GB, whereas your six hundred bucks at apple.com does not.