It's not really necessary if you are cleaning and oiling your blades regularly. Most blade washes just do that; wash the blade, they don't have any disinfectant in them, just chemicals to get rid of any buildup on the blades.
If your blades happen to get extra dirty, from mud or maybe some poo stuck to the bum or something else
You can just wash them in soapy water with a scrub brush. The key is to get them thoroughly dry and then oil them.
Sounds like you are taking good care of your blades so blade wash isn't necessary
(Don't worry, there are plenty of other doggie things to spend money on!
)