Am I calculating farming costs correctly?

I want to start/till a 4x50ft garden bed.

Doing it by hand costs me nothing. I have the shovel and rake. It'll take me 24hrs. I have to factor in cost of labour, right? I use minimum wage figures, which is $14 here.

So cost of tilling a bed by hand is $336.

-or-

I can rent a rototiller. Cost of 1days rent is $75. Cost of gas $20 (travel + operating fuel). Should take 5hrs labour (travel + the work). 75+20+70

So cost of tilling by machine is $165.

If time is no issue, what's my conclusion here? Tilling by hand would literally be free, but labour costs should be included right? Making machine till the cheaper option?