This is exactly what users should understand before they buy hosting. Unfortunately, users only realise this after they buy hosting because they are attracted by the large space offered by the host. The host knows this and that is why they offer such large space. There is usually other resource limits in their TOS which the user does not read properly and only realise when this sort of situation comes up later.

You are on a shared hosting server. There is no way that you will be able to use large amounts of resources on the server as this wil affect all other users on the server as well. This is why we always say that you will generally never be able to use the large space and data transfer they offer due to restrictions on other resources. Hosts have mislead users by offering such large amounts which the user will most liely never get to use fully.

The best thing you can do is to estimate your resource usage and buy hosting according to that and your budget. Don't keep looking for the largest space/data transfer for the least money. You will eventually get in trouble and be asked to upgrade or leave.

If you have a site that consumes a lot of resources and the site is important to you, don't put it on a shared hosting as it is most likely not suitable for a shared hosting environment anyway. Get something suitable for the site. If it cost more, than that is what you should pay.

I don't think this is considered high. The problem is not necessarily your site alone. If the server is overloaded with many other sites and there is not enough resources on the server in general, then you will also face this problem.