
Allow me to be the dissenting voice here. I believe you're being misled on this whole cover design thing, not in a malicious way, but it's still happening.
This is because, frankly, most authors are poor arbiters of what constitutes good cover design. I don't say that to offend anyone, but let's be real about what really works. Always look at the top sellers in your genre. What do their covers look like? Be honest in your assessment as a point of comparison.
Shayne is an obvious exception here, as a pro designer, but generally speaking there's a reason pro cover designers are paid good money by authors. It's because most writers have no clue what works from a design perspective. That's not their milieu. But, yes, the world is full of authors designing their covers, and you can tell that they have, not just in looking at their poor/homemade design, but also in what they earn in terms of income.
What's worse is, a lot of people believe their covers look good when they do not. A lot of authors leave a lot of money on the table in terms of sales because they think their covers are up to par when they're not. Fact is, people are generally not great at judging or honestly assessing their own handiwork. It almost always takes an outside eye... an outside TRAINED eye.
So, again...
Do not listen to other authors when it comes to cover design, unless they happen to be one of those outliers who can do both. Just know that... THEY ARE RARE.
Show me an author designing her/his own covers, I'll show you an author whose sales performance you likely would rather not emulate. Yes, there are exceptions... but, not very many. Which is to say, odds are VERY good you're not one of them. That's okay, no big deal, everyone can't be good at everything, just hire it out to a professional.
And...
No, your cover design is nowhere near this, even after adding typography (which is a whole other, and yet no less important, skill-set, btw):

If you can't see the vast gulf in design quality between these two, then to me that would further exemplify the point I'm trying to make.
The people in this thread, I'm sure, are lovely people - believe it or not, I'm a nice person too - but, respectfully, anyone telling you to do other than hire someone to design your cover(s) for you is wasting your time and money.
Again, I'm not saying anyone here is misleading you out of maliciousness - I believe everyone means well. I'm just saying, they're giving you a false impression of cover design quality when you hold your design up against the top sellers in your genre (which you always should).
In the interest of maximizing sales, yes, spending $300-$500 on a cover that can stack up against the Top 100 in your genre is probably prudent. Doesn't necessarily have to be that amount, but it's probably in the ballpark.
AND AGAIN - HUGE CAVEAT TO ALL OF THE ABOVE:
If you're not in this to maximize sales, then go ahead and play around doing your own thing. But, if sales matter to you, do not listen to other authors outside of the extreme outliers.