For some of the commodities, quotes may not be on 1 unit of a currency. For example, this ETF on Yahoo is quoted in 0.01 GBP. If I put price: "GBP:yahoo/XSDR.L" in beancount file, the price fetched would be 100x larger than the actual price.

I've also considered to introduce a separate unit for it, e.g. CGBP, and assume it is 0.01 GBP, but the problem then becomes that there is no easy way to fetch the exchange rate for this artificial currency.

It would probably be better to extend the syntax and support non-unit currency price, for example, price: "0.01GBP:yahoo/XSDR.L", and convert the price accordingly.