If it takes 5 hours to produce 0.0003 BTC

Then 33 x 5 or 165 hours to produce 1 bitcent

Which is worth less than a dime

Average computer uses 200 watts

That's 1 kWh every 5 hours (200W = 0.2kW; 0.2kW * 5h = 1kWh)

Or 33 kWh to produce a dime

Most people pay more than a dime per kWh

So this is a way to make someone else pay $3+ to earn you a dime

Why not just have them mail you their empty soda cans ... They will pay $3 in postage and then you can go recycle them for a dime

The economics are the same