It seems that your homepage ranking has fallen down, and one of your inner pages is ranking above your homepage. Anyways, whatever is the case, both the rankings won't give your good organic traffic.

I would advise you to focus on pulling traffic from different channels rather than focussing on SERP ranking.

Agree with C Rebecca.

As I checked your home page it doesn't have the word "Cheap" in any part of the page.

I have checked your landing page "interserver.net/cheap-vps" and I found it user/SEO friendly with keywords in title, URL etc.

I think it is better to target this page "interserver.net/cheap-vps"

Hope it helps.

Well proper landing page is interserver.net/cheap-vps because it is totally relevant to your keyword compare to home page. It provides more authenticity and visitors get the specific info what they want. Indirectly you bounce rate is also decrease by choosing this landing page. So use inner page for your link building campaign.