Speedtest shows that my download speed is 71.50 Mbps, but when I download something (a steam game for example) my download speed is 200-300 kb/s, I usually get 8-9 mb/s. I'm using wired ethernet. My ISP says the issue is on my end & there's nothing they can do about it.
Does this happen when you download something from any site? Or is it specific to a site or a couple sites (you mention Steam)?
If it is the former, then I am not sure what you mean by "I usually get 8-9 mb/s" (by the way, do you mean 8-9 megabit/s or megabyte/s...big difference...factor of 8 difference...I am assuming megabyte as 8-9 megabytes/s would be about equal to the roughly 72 megabits/s you are getting from Speedtest). Do you mean when you are do just normal browsing type activities that does not involves specific downloads (technically going to any website involves a download)? Or do you mean that you get those faster speeds with some downloads? And if it is the former, then it is likely either something on your end, a lot of coincidence of bottlenecks to various sites (highly unlikely), or a problem on the ISP's end.
If it is the latter, then see below. My first guess would be a combination of two items listed in point #2.
In the mean time, a couple things to keep in mind (sorry if you already know this...just offering it up in case you did not)...
1) The speeds your ISP states as what you will get are only from your modem to their main switching station. Once your Internet traffic from your computer "leaves" their network and enters the Internet "proper", all bets are off as your traffic is now going through switches/servers/etc that they no longer control.
2) Download speeds from specific websites will depend on the path your traffic takes to get to that website AND how the website itself serves up connections/dowloads. For the former, you might go to connect to say Microsoft's website today that gets there by one route that goes faster, but tomorrow takes a different route that goes slow. When you connect to a website, think of it like driving from New York City to Los Angeles. There are many different routes you can take which use roads with different speeds and different total distances traveled, plus they go through different cities/location which may or may not have traffic congestion due to accidents, rush hour, etc. The same basic thing existing on the Internet. For the latter, some website have multiple servers handling connections from users so they can handle more users and offer higher download speeds...others might only have one server that has to limit download speeds when there are lots of connections.