With so many domains you have easily 15k or 20k renewal costs every year. If you think that you can sell at least 1% of the names (18) for over USD 2000 it might be profitable. I would not only focus on hand-regging and also invest a bigger percentage of your budget on acquiring premium domains in a marketplace to reduce the recurring registration fees. #NoFinancialAdvise
If you're talking about 1800 being the quantity of domains, then it depends on the specific domains and the purchase price.
If you're talking about phone number domains that start with 1800 (like 1-800-FLOWERS.com or 1800FLOWERS.com), then it depends on the specific domains and the purchase price.
The last significant 1-800-blah-bla /com sale was back in 2014, for $2500. After that, most 800 numbers (pertaining to a telephone number) corresponding to a relevant .com sale totaled less than $500. So I would say it's not worthy.
Not to say it's not worth grabbing an exact-match toll-free 800 number to your DN, but not in a DN format, the actual phone line. I've done it for all my portfolio sites, just because 1-800 numbers are cheap and it looks awesome and easy alternate method for a client to contact you by.
With video-conferencing and most done via email nowadays, an 800 domain is pointless, even owning the real TN is just icing on the cake.
I don't see the point in investing in an 800 number in DN format unless it's the actual name of your company, eg. as the flower company that Ategy mentioned. And how many companies name themselves under an 1-800 umbrella? There is Freedom800 which run under a dot-com, but they specialize in toll-free 800 TN's.