What you are actually buying
The filing is standardised. Every agent on this page submits the same documents to the same registry and receives the same certificate, and the government takes US$150 of whatever you pay. The spread between US$439 and US$1,750 is entirely about what surrounds the filing: who answers when something goes wrong, whether the renewal was disclosed before you committed, and whether anyone will help with the bank account that the company is useless without.
That is why this list is ordered on published pricing rather than on reputation. Reputation in this market is mostly self-reported. A renewal fee printed on a public page is not.
Read the second year before you buy the first
The single most useful thing you can do is ask for the first-year total and the renewal total in the same message, before you pay anything.
Agents that lead with a low incorporation fee and will not state the renewal until year two are not necessarily overcharging, but they are choosing which number you compare on. On this page the entry prices differ by about US$1,300 while the three-year totals differ by considerably more, and the ordering changes depending on which one you look at.
Questions worth asking before you pay
Ask what the quote excludes, not what it includes. The usual omissions are the certificate of good standing, the apostille, the courier, and the ultimate beneficial owner filing.
Ask who actually files. Several agents in this market are placing the work with somebody on the island and adding a margin, which is a legitimate business but changes who you are talking to when a deadline slips.
Ask what happens if the company is struck off, and what restoration costs. It is a dull question that separates the field quickly.