Sorry A&C, 3hrs with two of us doing it. The other is an A&P friend.
Most of my 50hr check is visual inspection, which is quick. In fact most of the airframe inspection items listed in the 50hr list I do on every preflight check.
Cowling removal takes 5 mins for the top one, another 10 for the bottom one. (2 people are necessary) Prop spinner must be removed to safely remove the lower cowling without damage (most maint firms don't know this); this is 5 mins. Drain the oil out (including taking a sample for analysis) is an elapsed time of about 30 mins during which one does other things. Oil filter takes 10 mins including wirelocking the new one. Oil strainer at the base of the engine takes 20 mins including wirelocking.
Plugs come out in about 10 mins. They are iridium. The top ones are always spotless. The bottom ones always have some deposits but these come out with a special fine-wire tool. I run LOP all the time except climb so there is nothing else to clean. I'd guess 30 mins to do all 12 plugs.
We then run the engine with the cowlings off and check for any leaks.
The price list cost of a 50hr check on mine is £220+VAT I think, which is only a few hours' work. So it's about right.
Evidently some planes are easier to work on than others.