You got that reversed. Buying from DR everything is more expensive, airlines, hotels, etc. You cannot even get into JC Penny website, less buy there (and it was possible few years back). Now I have to resort to VPN use. Thanks God Kohls is still fine.
Airlines no longer do point of purchase price differentiation on USA-DR routes. Too competitive market now for that. And if you buy RT from DR to USA, you will actually pay more than if RT originates in USA because you pay DR taxes even on US-DR leg. But if you buy two one ways, you can save the taxes on US-DR leg (by booking two OWs instead of one RT).
Resorts, you pay more for resorts than if you book from abroad. Easily verified by going to most hotel online sites from DR and checking prices, and then clearing browser cookies and cache and going through VPN (preferably Spain, Germany or UK IP address) and checking prices again, the difference will be noticeable (much lower prices).
You only get special DR prices if there is some promotion being run, especially in off-peak times. But usually those promotions are through a special access links, and those links are clickable from anywhere in the world (getting that promotion as well).
It is a known fact that Dominicans pay one of the most expensive rates for resorts of all tourists (because they are close. The farther the tourists come form, the lower the rate they pay). There is a Memories splash promotion on one of the group buy sites (viagrupo, I think, or gustazos). It still costs more with their 57% discount than the rate I get by booking directly via TUI (Germany). Imagine the rate Dominicans pay without a discount. And still yet, my cheaper rate bought through a German TTOO is for premium room while the group buy rate is for run of the house room.