N inexpensive substitute for truffles

Yes, yes there is.

Black truffles are dark, earthy, sexy in flavour. Renaissance writings compare them to 'unwashed slatterns' and 'bedchambers, rooms of sexual congress, unaired and reeking of the recent activities contained therein.'

White truffles are lighter in aroma and flavour, with distinct garlicky notes. Each has their place--black works better on its own, white works better as an adjunt or finishing note to a dish. I am personally partial to white truffle oil drizzled on cured duck breast, or a black truffle risotto with charred endive.

I think the truffles that are exported are of better quality on average than what you'll find on the european market. I've never tried the american ones consciously (they're not imported to Europe as far as I know).

You could also take into account that the fresher the truffles are the better the quality, so in theory it would be better to eat american truffles in the USA and european truffles in Europe.

Given the mind boggling price differences and the supposed high quality of the stuff found in the forests in Oregon, you're likely going to be well off picking the local stuff.