What makes a difference between high-cost cloud providers and low-cost ones?
@jasper, and welcome to DevOps SE!

While your statement can be confirmed by other voices, it's very hard to x-ray price policies of a company. It's a complex gameplay always driven by many factors and decisions and a question about pricing policies of Digital Ocean vs. AWS might be a good and on possibly well on topic question at Economics SE.

For example, one could argue to find facts supporting the evidence of Digital Ocean currently being cheaper that:


Docker, Inc. is in a situation where it cannot afford losing customers, so maybe they a cautious and prefer lower margin to attract customers.
Amazon is the market's prime with top notch customers from overall industry and government: stability, seriousity and credability are way more important than money, especially given that expenditures on information technology is only a (small) part of industrial budget planning. Also, Amazon has many more data centers and is as whole investing billions to AI technology ($0.8b in 2017, almost complete estimated market value of Docker Inc.), custom data center hardware, buying startups etc.


Please consider making your question more specific in the DevOps SE site context to get more answers.

This sort of decision is possibly best to elaborate together with the customer, collect their business requirements if price is not the only one requirement and assess risks. 

Further reading/related business topic: due diligence.

Additional note: one might think, AWS would have way more customers than Digital Ocean but at least as of 2017 this was not the case. 


Digital Ocean: 1 million users in 2017
AWS: more than 1 million users in 2017