Be aware that the Domain Authority numbers were reconfigured/recalculated here just recently (Feb 2019?). So you're going to find a bunch of people offering DA's on different forums.
Spending the money on high DA's is not worth the effort. All you really need to do is audit your website, determine your DA/TF (if you wanted) and then aquire links for anyone that is above your numbers.
Getting a DA 60 to link to your site when you have a DA2 doesn't do any good. If you must follow arbitrary numbers, you should be stepping up in 5-10 DA incriments.
All that said, with our SEO clients, we don't use DA at all in our reach out campaigns. We strictly look for links related in the industry and then contact those sites with content etc. Blinding purchasing DA links does have an instant effect, but the results are hard to sustain.