In Singapore, there are three tiers of SEO companies. Companies of each tiers designed their SEO service packaging depending on the number of keywords, link requests, bookmarks, content submission, monitoring and other services. The seo services pricing Singapore is based on the type of package from the tier of company you choose.
Depending on your business value, choose the SEO service provider from the specific tier. Wisely pick the package. If needed, consult with them or a pro SEO auditor so that you can get 100% ROI. Nowadays, SEO is a guaranteed service which was impossible to ensure previously. Do have a word with the company and sign up with them.