How do you define meaningful? For a single novice user this would be the cost of hardware (substantial), opportunity cost from delays in delivery of hardware,

How do you define meaningful? For a single novice user this would be the cost of hardware (substantial), opportunity cost from delays in delivery of hardware, decaying returns with exponential increase in difficulty, cost of electricity and opportunity cost. Then it needs to be ascertained if they are mining a commodity or an investment. That is mining to sell (similar to farming and mining minerals, metals etc.) or are they looking to hold it for long periods expecting an appreciation. The later has other practical implications. For the majority of prospective miners, these costs are huge and have little to no chance of breaking even. Arguments could be made for or against the profitability from speculation/long term holding, but that is beyond the scope of most people's definition of meaningful.