I don't think we have a way to reliably estimate the value of non-transactional goods, because by definition nobody gives them a price.

but an estimate could be had if you use an imputed price of similar goods/services that _are_ transactional? So the problem reduces down to counting these events - perhaps a survey and such could be used to estimate their frequency etc?

Why are you so pessimistic? Just because something is hard and you get big error bars doesn't mean we can't do it at all.

If you wanted to, you could look at eg black market prices for kidneys to get an estimate for how much your kidney is worth. Or, less macabre, you can look at how much you'd have to pay a gardener to mow your lawn to see what the labour of your son is worth.