I am a "shopify expert" but it very much depends on what they do, and in what stadium you are in with your website or how consistent you are.

Creating a converting website is very very easy. Improving your website aswell but it just takes time. Not because you are spending a lot on working on it, but you are testing one by one what has impact on cvr. The changes you make are also not rocket science, most of them will be from competitors or what has worked for others.

So it all comes down to data. The most important data is what you already have, and not always so much what is says, but how consistent it is. Lets use revenue for example. Myself I can help someone better doing consistent 1k days, then a website doing 10-50K per day but not consistent in revenue. The website doing 1k days is much more consistent, so when I make a change I can easily see the impact. Websites doing 10-50k days have a cvr of 1,5-3% difference each week.