I think one of the take home messages here might be that due to this difference in effort and other factors having to do with privacy and the fungiblity of Bitcoin in general: do not reuse Bitcoin addresses. Bitcoin addresses should be used exactly twice: once to fund them and once to spend them - then never used again.
There's plenty of addresses with hundreds or even thousands of transactions on them, so what you're saying is that bitcoin isn't secure enough and those addresses are more at risk?