This is a very complicated/dense question that depends on a lot of factors so I'll be making some assumptions.

First let's address the case where it is a large corporation:

- The risk of the 3x-dev leaving wouldn't be much as it is a large corporation and hence there are mechanisms at place that are ready to fill the 3-devs gap he will make if he left at any particular time.

- It is very economical to pay 3x salary for the 3x-dev as it saves on managerial costs.

- Promoting the 3x-dev to a team leader or a senior position is a good strategy as it will increase retention chances with him and also promotes sharing experiences and knowledge.

* Hiring 3-devs is rather a tedious task and have a significantly higher managerial cost, and the risk of them leaving is even higher as they won't feel that much special, hence no early rewards and the eventuality of them looking for other options out there.

* I daresay there is a statistical certainty that the 3-devs won't be on the exact same knowledge/experience level which will result into communication overhead that includes the assumption that they are good at communicating in the first place.

Office politics will make things even harder if you promote one of those 3-devs - that you hired at the same date - to reward a personal achievement of sorts.

Now in a small company/startup:

- Hiring the 3x-dev involves a high risk if he's not rewarded often with more than just a bonus or a salary increase, like a piece of the company that he helps building.

- Hiring him will cut down on managerial expenses greatly, and will result in a much smoother development process.

- There's no body that of concern to compete with head to head and even if there were, they are supposedly experienced and professional enough to keep things light between them and focus on delivering results.

Hiring the 3-devs have a very high risk if they _are_ rewarded equally - which you hired them at the same date - simply because you are normalizing their efforts and hence creating a class of sorts which can and in fact will backfire. Now if you decided to pay attention to every developer separately, that might create jealously, which can be a positive thing, but it largely depends on the company culture/atmosphere you have and it is quite tricky to maintain.

* There's a managerial overhead that won't be easy to maintain since this is a small company and you yourself have things to do better than maintaining logistics/communication and team spirit.

* The fact that this is a small company by definition will require a diversified skill set, flexibility, and not just willingness to learn but rather knowing how to consume knowledge fast and turn it into an actionable skill, while this is questionable although highly likely, your 3-devs will find it difficult - and quite overwhelming - to take over the many tasks that require different skills in the tight time window and stress that comes with all small companies. But this also depends on how you structure your company culture/political-atmosphere, and yes there will always be company politics whether you like it or not, even if you intentionally and consciously try not to develop them.

All in all, I believe that every environment and work place is quite unique. But from personal experience over multiple quite different industries, quality comes before quantity.

So my short summarized answer is to go with the 3x-dev and give him 2.0x-2.5x if it were a large company with short period rewards, or give him 1.5x-2.0x if it is a small company with emphasis on long term benefits/interests coupled with exciting/teasing short term rewards.