ULF can be both addictive and expensive. But you might think of it also as an investment since you can easly re-sell the equipment if you need or want to, often for more than your investment. Because of the limited supply of new cameras and holders in the ULF sizes used equpment sells very fast. And that includes lenses as well.
If you buy an 12X20 Canham tomorrow for $6000 it will probably be worth at least $5000 five years from now. And used vintage equipment has been going up in price for years. You can not say that about a lot of photographic equipment.
So just tell your mate that purchase of ULF equipment is like putting your money in a saving account.