Another vote for "2 person" tent for one person. You won't notice the extra pound or so while riding, but you'll definitely notice the difference in comfort when you sleep. I put all my bags inside the tent when I've bike camped, what manufacturers call a 1 person tent leaves no room but you and a sleeping bag.
As for cost, tents are one of those things you should consider buying used. Same goes for bike travel cases. Lots of people buy either of these for a trip, then decide it's not for them. Craigslist often has them. I bought my Big Agnes 2 person tent at an REI garage sale for less than half price of a new one. It had a small tear that was easily repaired.
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If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.