Yes, properly checking an Ethernet cable is expensive. The expensive testers will inject test signals at various frequencies and will then measure attenuation, crosstalk, resistance, capacitance and various other parameters.
That is not something a cheap tester can do.
A poor-mans test might simply be to test if the cable works.
Take two computers with gigabit ethernet. For this I would recommend Linux as operating system, booting a live system is enough. Preferably use machines that use good network adapters. Intel adapters are generally considered best.
Install iperf or net-io.
Connect the two machines with a known good cable and set up proper networking.
Run tests in both directions to get a baseline.
Then you can do the same tests on your suspect cables.
Generally, in my experience, ethernet cables are very robust. The main weakness lies in the connectors. The latch is generally the thing that breaks and makes the cables useless. Sliding across a sharp edge also causes obvious damage. Sometimes we have cables with visible corrosion on the contacts. A lot of cables that look ugly, with visible kinks and sometimes damage to the outer sheath still work fine. All that is for S/FTP cables. UTP Cables are a lot less resistant against damage, and that is the main reason we avoid using them, even though they are fine for gigabit Ethernet.
For permanent cabling, the connections at the patch panel or the jack are what fails, but that is very rare. Out of several thousand RJ45 ports at my workplace, we had to repair maybe 5 in the last several years. Other than that, all repairs we had to do were due to someone cutting the cable.