In 2018 Ebay made $10.74 Billion in revenue
In 2018 Shopify made $1.07 Billion in revenue
when they run out of places to efficiently deploy capital then they become a standard tech bluechip
I can connect my Stripe account to Shopify, but I can't do that on eBay.
OP didn't say anything about profit.
Similarly, Stripe does not recognize the full value of every transaction as revenue, only their fees.
Shopify's revenue from https://investors.shopify.com/financial-reports/default.aspx is $362 million and their GMV is $13.8 billion. Looking at their fees at https://www.shopify.com/pricing , they charge between 2% to 3%. This seems to be about right.
This is a superficial look but, I think to your original question, the revenue should be comparable.
From the growth numbers listed in the report, the gross merchant volume (and therefore the Merchant Solutions revenue) is increasing so maybe more merchants are being successful or the existing successful merchants are selling more. The Merchant Solutions revenue is growing about 18% faster than Subscription Services.
Shopify seems to be trying to make more merchants successful (more merchants selling more goods) versus just making it easy to open (and close) unsuccessful stores.
Hopefully Shopify is able to capitalize on increase in merchandise volume if they haven't been able to negotiate a good deal on the payment processing fees themselves. While they might make profits (and not just revenue) from their monthly fees and their App Store, I just can't imagine a merchant platform which does not capitalize on gross merchant volume since that's where the significant profit comes from (like eBay, for better or worse).