I don't own any .travel names but judging by past sales at NameBio it will come down solely to demand.
These are the only comparable sales I found:
miami.travel 400 USD 2019-06-20
ostsee.travel 10,760 USD 2019-03-15
paris.travel 5,950 USD 2017-09-03
puntacana.travel 4,200 USD 2017-04-20
siam.travel 1,240 USD 2016-09-09
mallorca.travel 2,866 USD 2015-06-21
newyork.travel 5,000 USD 2013-05-22
bangkok.travel 2,000 USD 2012-10-17
crimea.travel 5,000 USD 2011-01-18
europe.travel 5,000 USD 2009-03-24
From this I glean that there are 10 recorded sales (of similar names) in 10 years. That's not many.
A premium name like Paris went for only $6k, while Ostsee holds the record at almost $11k! Miami went for only $400. [Obviously there will be some unrecorded sales, but we can't comment on them.]
So, sure - there is the
potential of high xxx to low xxxx, BUT you need to consider how often these offers might come up. There is a good chance that if you don't do a deal now you may not get another offer. But that is the risk we take on a lot of domains like this. You might consider doing a deal on 1 or 2 of the domains to cover some costs then hold the better 1 or 2 for a potential pay-day. Just a thought... I'm not sure what you're paying for renewals but last I looked .travel wasn't real cheap - renewal costs should be considered.
All the best.