I spoke to my gf who had a wishing well and she said the average was $50+ but she also said that she wouldn't have minded what it was, it was purely to save people spending money on stuff they already had and they didn't really need anything else for their home. So if people felt as though they wanted or needed to buy a gift this was another option, however they did have people who still gave presents and that was fine with her too.

I think the wishing well is a great idea especially for long standing couples or those who might not otherwise afford a honeymoon etc.

*hugs*
Cailin