I feel your pain! Two years ago I was given a 12.5hp riding mower for free.
Replaced the starter, tune up, blades and oil change and I'm mowing for less that $150 US.
Season two, oil change and plugs. Season three it drops a valve, sucks it into the cylinder and
pokes two holes right through the head.

Luckily I found an online parts vendor here in the States
with the head I needed on sale for $105!
Sometimes things actually do work out.