Has been a standard currency here in Oz for years. Called mates rates. If you need a bit of work done and one of your mates comes round to sort it out. The payment is decided something like this? Yes mate can do that for two slabs of beer (slab being a case of beer). So depending on the size of the job depends on how many slabs are required in payment. For very small jobs it is then decided on shouts at the pub. For larger jobs it then becomes a BBQ with all the families attending.
That's the way the mop flops.
My thanks to Brian for this site.