Or if you pay what is the price?

It's free

There is NO Price to visit The Menil Collection. During Special Events, a valid Event Pass is needed for food and wine hosting, and color-coded stickers to see Private Collections. Event Passes are donated by their Foundations and are awarded by their respective members. Donations are not encouraged or needed at The Menil.

If you pay what you want, they do not charge the entrance, it is like a donation

You pay what you want