The pro-prop-8 side spent $39M. The passage of the amendment caused the state to stop recognizing 18,000 previously-legitimate marriages. So if you count only immediate effects, his $1000 contribution works out to 0.46 marriages, or destroying the marriage of about one person. Is the emotional harm done to that person worth hundreds of thousands of dollars? It's at least comparable.
In fact I think the harm done to Californians and other Americans by the passage of prop 8 is vastly more than is implied by that simple calculation. I'll just link to my other comment: https://news.ycombinator.com/item?id=7525692
Do you believe that you're making a good-faith attempt to understand how prop 8 caused actual harm to people, and how Eich bears some responsibility for that harm?
For this purpose you don't even have to accept that it was a net negative; you could even believe that prop 8 was overall positive for society. Just that it also caused some harm to some people, and that Eich suffering harm as well is not some crazy unjustified notion, but can be talked about in the same way.