What amount of funds you will hold that you will start getting worried of having to buy a hardware wallet? Can you give me a number? 5000$ 10,000$? What advice would you give someone under 1000$ of asset in hold?...
o_e_l_e_o has already covered this very well, so there isn't much to add.
An amount such as $100 isn't valued equally in all parts of the world and by all people. For some, it's their entire monthly salary, but for others it's something you spend on your friends on a night out. There isn't really a threshold that needs to be crossed for you to start using a hardware wallet or cold storage. Take any amount. Let's do $100 since that's what I mentioned earlier. Imagine that $100 worth of BTC in your possession. If you lost it tomorrow, would you a) laugh about it because it's such an insignificant amount in your life that it's not worth worrying about, or b) you would be holding your head in disbelief at what you have done not knowing if you will be able to put food on the table one week from now?
If your answer leans more towards "b", I would consider upgrading my security to make sure I decrease the possibilities of losing my coins.